"What do you think you're doing?" - Don's voice sounded behind his back.
Mikey froze without turning. His eyes were stinging from trying to hold back the treacherous moisture and he didn't want Donatello to see it. He felt his brother stop just one step behind him.
"Donny. Would you please stop sneaking up on me?! I so gonna get a heart attack one of these days!"

'No, you're not" - Don grinned. "Your heart can handle it - I'm your doctor, remember?  And don't try to change the subject. What the hell was that?" Don reached to touch Mikey shoulder in a comforing gesture but at the last moment changed his mind.

"Well, that? "- Mikey gestured toward Raph's closed door, a slight strain in his voice complemented by his gesture - too brisque a gesture for a non-challant ninja - "That was Leo getting rid of dead weight. Because apparently, this is what I am. Third wheel. No one finds me.. interesting."

"That's not true" - Don quickly said.

"Oh, really?!" Mikey turned to face him, the stirring ire whiping any traces of tears from his expression "What was that last time then? You couldn't have kicked me out faster if you were Flash!"
Don bit his lower lip: "Yeah I know...I'm sorry, Mikey. I just... panicked, I guess."

"I tend to have that effect" - Mikey whispered, returning his gaze to Raph's closed door. His lower lip started to tremble ever so slightly. Donny eyed him intently, noting all the tell-tale signs.

"Care to share what happened?" Donatello asked, careful not to let any accusing tones infiltrate his voice. Mikey stared at him in response. "Oh no... Tell me you didn't do anything stuid?" 

Mikey just sobbed.

Don saw that his vibrant brother was on the verge of tears, and pulled the youngest into a light embrace, stroking his head, like Mikey was a small child. The tone that he spoke in, was also a signature adult-to-kid talking.

"I know you've been obsessing over Leo for a while now, Mike. But this wasn't the right time to approach him. He can't even think of strolling your way before he clears things with Raph. That would be cheating, and his honour wouldn't let him. He didn't say "no", right?"

"He didn't say "yes", - Mikey whispered. - He just ran away".

"And that's a good sign, right?" - Donnie made his best to radiate optimism hoping that it would be contagious.   - "If Leo wouldn't be interested in you, he'd say that straight, wouldn't he? You've just chosen the wrong time, Mike-ster."

"Don't. Just don't" - Mikey's voice sounded muffled as he hid his face, pressing it to Don's shoulder. "I know it was stupid. I just cant stop thinking..." He raised his head and locked his gaze with Don as if trying to pry answers from out genius' dark orbs. "Why can't I stop thinking about it, Donny?"

Donny shifted uncomfortably. He never had a bees-and-flowers talk with his siblings, but he always asumed that such talks were not his prerogative. "It's.. It's the mating season, man. Every now and then it just fills you with all that... urges.. and.."

"I know how it is! I'm not a baby, Donny, I've been through this before! It's never been so... intense."

"Hmm" - Donatello mused. Now that Mikey mentioned it, he realised that he himself was having a hard time concentrating lately. The possible explanation surfaced quickly, but the hypothesis stil needed testing of course. Seeing that Mikey was waiting for an answer, Don decided to voice it nevertheless.

"It's just a hypothesis, but maybe it's because now you know that it is possible. You've seen a proof that this kind of release may be available for you and this encourages your psychosomatics. You're body just doesn't want to be fooled anymore."

"But it is NOT available!" Don't gestured him to keep his voice down and Mikey whispered "It is not! He just blew me out into the water! How do I make my body understand that?!"

"You have other options" - Donny didn't know he was going to say it, yet there he was.

Mikey shook his head and whispered " I don't wanna turn you into a substitute of what I can't have. And I don't wanna be a substitute myself"

"Funny for you to say so after last time in my lab".

"Dude! YOU have kicked me out!"

"What did you expect? For heaven's sake Mikey, you were jerking off to Leo's video in front of me! How do you think that made me feel?!"

"It was your idea! What did you expect me to do? Take written notes?!"

Agitated whisperes filled the corridor that suddenly turned to be a proper place to discuss the most delicate issues.

"You could have asked me to join you!"

"Would you have joined me if I did?"

Agitated, brothers stared at each other. Finally, Donatello said: "Well, looks like I joined you anyway. So my point stays." Don now had a rare occasion to see Mikey blush. Pinkish hue appearing on his sea-green ñheeks made a very nice color contrast.

Unexpected for himself, the olive skinned turtle pulled the younger to him and kissed him catching Mikey mid-word and off-guard. Before he thought to resist it, Mikey found his lips opening eagerly for Donnie's intrusion. Mikey felt Donnie's tongue moving around inside his mouth, caressing, testing, and melted agains his brother body, letting himself be carried away however briefly. The kiss was rather clumsy and hasted, but the orange banded turtle had never been kissed like that before and  it was like coming topside for the first time - his brain exploded from the awesomeness of it.

Yeah, and his body was definitely not going to be fooled. Mikey couldn't hide a dissapointed sigh when they finally separated.

"You wanna go over to my lab? We can test my theory..?"

Mikey cast a last glance on Raph's door - no evidence of anything moving there, - and said "Promise you won't kick me out?"
"Never again"- smiled the genius and led Mikey away from the shards of his broken hopes.

****
Once they were in the lab, some of Mikey's nervousness returned. He licked his lips, watching Don close and lock the door behind them. 

"You sure you want this dude? I mean, I'm ok if you don't, you don't have to do this to prove me anything"

Donny started stripping of his gear. " I'm not" he said. "Are you backing down?"

"No! Of course, not! It's just... I just don't want things to get weird between us and..." Mikey found humself unable to go on, as Donnie's hand covered his mouth, invoking memories that made the orange-banded turtle hot and meek. 

Don was quite aware of what he was doing, when he ran his free hand up and down Mikey's plastron and husked into his ear slit "You talk too much, Mikey." - Mikey literally shuddered at the words, - "and I never thought I was gonna say it, but you're overthinking it. On the cot."

Mikey obeyed and watched his smart brother rummage across the room fetching everything he needed for whatever he had in mind. "So... How you wanna test it?"

Donny set up the small monitor again and returned to his slightly embarrased sibling. He stepped into the space between Mikey's knees and cupped his face, kissing him. "I thought about putting sensors on your sculp to measure your brain activity, but I think that would kill the mood. So it's just a couple of observation cameras. I'm gonna expose you to  a mixture of various visual and tactile stimuli and after, when I've seen the tape, I will analyze your reaction, compare it to mine and define the common denominator. And for the purity of measurement it is vital that you don't touch yourself. Can you do that for me?" All the while that Donny spoke, his hands glided up and down Mikey's legs while he retained eye contact.

"Wait-wait... You're saying you want to show me some porn and watch my reaction? And I'm not allowed to touch myself?"

"Basically, yes. Let me do all the work."

"Isn't that exactly what you did last time?"

Donny grinned and leaned in to nuzzle at Mikey's neck, the later automatically tilting his head to give the olive-skinned turtle a better access. Mikey closed his eyes, when Don whisoered "Sometimes I forget how smart you are, bro. Yeah, it's what I tried to do last time, but last time I miscalculated my own reaction and since I obviously can't stay out of it, this time I'm not relaying on my eyes for observation and filming it instead"

"Wow. I'm ... hurt. Am I .... just a lab rabbit to you?" Much as Mikey wanted to sound offended, it was hard to achieve it when his body was trembling with a confined churr.

Donatello straightened to give him a look and Mikey immediately wanted to scream for his hands to return where there were a second ago.
"No. You're not a lab rabbit. But I need to figure out what is happening to us. To all of us. If this is any consolation to you, I'll be as a lab rabbit in it as you. So, can you restrain from touching yourself?" With that, Donnie's hands thankfully returned to their previous occupation. 

Mikey bit his upper lip. "No promises, dude. But you know, it's creepy. And you know, what's uber-creepy? I still wanna do it and I start to find your science talk real sexy."

"I see." Donny's head dived in to nuzzle the sea-green neck some more before he reached up and purred at Mikey's ear slit " Looks like I will have to contain you otherwise". With that, Don took Mikey's left wrist and deftly secured it with the cot straps. The orange banded turtle didn't protest, and soon the right wrist followed. Mikey gave it a test pool - the straps allowed him some movement, but not enough to reach his now bulging slit. 
"Oh no!"  - Mikey all but crooned "Doctor, what are going to do with me?" - He meant it as a joke, but it came out so lustfull that Donnie churred in responce. "Relax, man" he said, pushing Mikey in the chest so that he leaned back onto the wall "You're in for some serious fun".

The genius left Mikey's side for a moment to adjust the display for a better view, check the camera positions and kick the playback into action. That done, he sat beside his tied brother.

Despite Michelangelo's expectations, first shots that appeared on the screen featured no mutant turtles. There were boobs. And dicks. And lots of skin. 
"Dude, naked humans?! Ewwww!"
"It's a control sequence, I need a base for comparison" 
Mikey shot him an incredulous look and shook his head.

Luckily, the disgusting show didn't last long, although... "Dude! Is it Animal Planet? What's wrong with you?" 
"Galapagos giant tortoises in mating... nothing? Really? Just checking..."
"Do you..?"
"Just checking, Mikey" - Don said, carefully fixing his gaze on the screen. Mikey chuckled "This is rich"  - he murmured, but decided not to dwell on it - the show on screen just turned to the part he was anticipating and there was too much to dwell on on the screen at the moment.
By the look of it, Donny had put together several sewer recordings. Must be a selection of his favorite moments, Mikey mused.

He was looking at his older brothers kissing. Raph's hand was cupping Leo's neck, keeping  his head slightly turned, while his other hand was playing with the leader's tail. The two turned a little and Mikey saw that trapped between their bodies were their freed cocks and Leo was pumping them slowly, his hand sliding off unable to truly close around both their members. Precome was oozing out and the sleaky flesh was glistening in the dim light of the emergency lamp.

Mikey felt his cheeks heat up as he watched it. He was parly aware of Don's studying gaze that he turned his was from time to time.

His slit was bulging now and it had begun to feel really uncomfortable just to sit. The orange banded turtle turned to his captor to ask for assistance, and suddenly he was looking at Don's quickly hardening member, raising proudly. Donnie's hands were lying flat on his legs as he appeared to be straining to keep them from moving.
Mikey felt a heat wave rush through his system and his own dick slid smoothly out of his confines. "Don.."

The genius didn't let lim finish: "Eyes on screen, Mike" he told in a no-bullshit tone he was usually using to keep his siblings still during medical manipulations. He reached up and turned Mikey's head back to the screen, emphasizing the point.

Mikey obeyed and was now watching Raph pulling one of Leo's legs up to his waist, sliding a hand along the inner side of his thigh. Leo clasped the emerald shoulder to keep steady as his rebellous brother lined his erection up and prepared to breach his walls.

Mikey absentmindedly reached to stroke his now rock hard erection. The restrains cutting into his wrists reminded him of the rules he agreed to but strangely only added to his arousal.
"Mmmgmm... Donnie, please"  - he begged, unable to tear his eyes from the display, where Rah was now holding Leo's both legs and impaling him onto his cock. The two on video staggered to the nearest wall, where Leo's hands found some pipes to hang onto, as he threw his head up, the intense pleasure on his usually impassive face.
Mikey wiggled a little trying to get closer to Donnie's leg beside him - he now felt heat emanating from it.

Suddenly Don was there no more - he was kneeling before his brother, gliding his hands up sea-green legs, keeping his head down not to obtrude the view.
When the deft fingers reached Mikey's croth the later let out a long satisfied sigh, having at last something tactile to concentrate on. Don licked his hand several times and started pumping his brother watching his face expression intently.  Mikey closed his eyes and arched back as much as he could considering his position, his expression much similar to Leo's on the screen.

Don leaned in and took the tip into his mouth. Mikey's eyes snapped open and he looked down at his bro. Don grinned around his cock and doubled his pumping efforts. Mikey churred, twisting in his restraints. It didn't take long for him to reach the endpoint.
Don felt the climax approach and moved aside just in time, milking Mikey off with his hand, as he landed beside him on the cot and sealed his lips with a kiss.  Mikey came moaning his name.

As Don made sure that his brother was spent indeed, he walked off to wipe his hands and turn off the playback. When he returned, Mikey's eyes were already open and following his movement. Don made no attempts neither to hide his dangling erection, nor to take care of it.

"Dude, - Mikey exhaled, - what about you?"
Donnie leaned over him, his hot flesh sliding across Mikey's thighs, and cut off the strapps holding his wrists.

"I think it's time you return the favor" he said, kneeling at both sides of his sibling and bringing his erection closer to the other's face.

Mikey cast a hesitating glance at his face, then licked the offered flesh tentatively.
Don churred.