This has to have the most detailed kissing scene I've ever done in my short life! Sorry if I messed anything up, too (15, virgin, hasn't had first kiss, hasn't had boyfriend OR girlfriend), please don't kill me!
Toshiro had been visiting the world of the living a lot recently. The reason was unknown to Toshiro's fellow soul reapers, but they noticed that he always left exited, and came back happy, they didn't push for answers since it was rare for the short captain to show a positive emotion.
Currently, Toshiro was walking randomly around the world of the living with Ichigo's sister, Karin. The two had become good friends. VERY good friends. Whenever Toshiro visited, he went strait to the Kurosaki household to pick up Karin, and they would either go out for ice cream, or go to the soccer field to play a game.
When they were around others, Karin and Toshiro would mainly ignore each other, but when they were by themselves, Karin and Toshiro would walk closer together, joke around, and occasionally have a more-then-friends moment. The last was never mentioned, they wouldn't talk about it and they'd act like it never happened.
"What's that?" Toshiro asked, seeing Karin pull out a small packet.
"It's gum" Karin replied, "watermelon flavour".
"Watermelon?" Toshiro blinked, "...can I have some?"
"Sorry, this is the last one" Karin apologized, poking her tongue out to show the last piece of gum.
"That's alright, we can share" Toshiro grinned.
"Sh-share?!" Karin yelped.
"That's what I said, wasn't it?" Toshiro smirked.
"B-bu-but-bu-" Karin stuttered, she was cut off when Toshiro turned her and quickly pressed his mouth to her's.
Toshiro took advantage of Karin's gasp of surprise and pushed his tongue into her mouth to steal the gum. Karin quickly got over her surprise and moved the gum to the opposite side of her mouth to keep it away from Toshiro before biting Toshiro's tongue to try and make him leave, but she only got a bite to her tongue in return. Karin flinched at the slight pain, and Toshiro went for the gum again, this time successfully getting the gum into his own mouth before pulling away triumphantly.
Refusing to give up, Karin pulled Toshiro closer to her -he had gotten a little taller in the past year- and forced her tongue into his mouth, but Toshiro had cleaverly hidden the gum underneath his tongue, so Karin had to try and push his tongue away while she went for the gum.
Karin had gotten her gum back eventually, but it had somehow been forgotten at the side of her mouth when she found herself continuing to move her tongue around her white haired "friend's" mouth, while Toshiro continued to do the same to her's.
This continued for a while, and the couple had started to thank the fact that they were in an ally, but then they found themselves forced apart.
"What the hell are you doing to my sister?!" Ichigo yelled furiously to Toshiro.
Toshiro couldn't think of a reply that wouldn't get his head smashed in, so he pushed himself out of his gigai before grabbing it and flash-stepping to Urahara's shop, knowing he might just loose his life if he stayed.
Everyone in the soul society stared, shocked to find the tenth division's captain gasping for breath as he exited the senkaimon. He knew the substitute soul reaper wasn't too far behind him, so he fled to the tenth division.
"Captain? What's gotten into you?" Rangiku worried as she watched her captain barricade the door and windows before hiding under his desk.
"When Kurosaki gets here, you never saw me, got it?" Toshiro whispered to his lieutenant.
"...O...kaaay..." Rangiku was completely confused about the situation, and was even more so when her captain his his spiritual pressure completely.
Suddenly, Ichigo appeared in the room, with his bankai activated.
"Wh-what?!" Rangiku exclaimed.
"Where's Toshiro?!" Ichigo growled, "I'm gonna wring his worthless neck!"
Scared for her life, Rangiku pointed to Toshiro's desk, which was practically shaking with fear.
Ichigo lunged at the desk and pulled the short captain out by his neck.
"What did you think you were doing?!" Ichigo questioned.
"I-I-I d-don't kno-know wh-what you-you're t-talking ab-about!" Toshiro gasped, trying to get air back into his lungs.
"Why did you kiss my sister?!" Ichigo glared, Toshiro could see his urge to kill.
"He what?!" Rangiku gaped.
Ichigo ignored her and waited impatiently for Toshiro's answer, "tell me!"
"I-I wanted some g-gum" Toshiro refused to look at the room's other two inhabitants, knowing he was blushing.
"What?" Ichigo blinked, he was confused.
"Karin had the last strip of watermelon gum" Toshiro clarified.
"Watermelon?" Ichigo repeated.
"Ha! I knew you liked watermelon, but not that much!" Rangiku laughed.
"What's that supposed to mean?" Toshiro glared, picking up something between the lines.
"You'd never kiss anyone unless you actually liked them" Rangiku grinned, secretly she had a plan, "but since you don't like anyone that way and never have, you'd only do it for something you wanted".
"You took my sister's first kiss for a piece of gum?!" Ichigo growled, Toshiro saw small fragments of his mask appearing.
"N-No!" Toshiro paniced.
"Oh, so you like her then?" Rangiku smirked.
The hollow mask started appearing faster.
"I'm going to lose my head either way" Toshiro concluded, "so...yeah".
"Yes!" Rangiku cried victoriously.
Ichigo's mask suddenly stopped forming.
"H-huh?" Toshiro blinked, surprised by the fact that he didn't have a hole in his chest.
"You seriously like my sister?" Ichigo questioned seriously.
Toshiro gulped and nodded.
"...You'd better not hurt her" Ichigo warned before releasing Toshiro and marching out of the room, deactivating his bankai along the way.
"...What just happened?" Toshiro wondered, not bothering to move from the spot where he'd landed.
"You just got your future brother-in-law's blessing" Rangiku smiled.
"What?" Toshiro jumped.
"He approves" Rangiku repeated, "now, tell me! I wanna know about my captain's first kiss!"
"Wh- sh-shut up!" Toshiro glared before leaving the room and going in the opposite direction of Ichigo, since the orange haired male might change his mind.
Within an hour, the news of the white haired captain's love life spread around the soul society, and some had tried to find him and congratulate him for living through Ichigo's attempt at murder, but they couldn't find him anywhere.
Toshiro smiled sheepishly as he explained what'd happened to Karin, including the fact that he liked her, ignoring the flaring spiritual pressure of her older brother coming from the bushed nearby.
"Well...congratulations" Karin laughed, "you're pretty lucky to live through that, huh?"
"What?" Toshiro gaped.
"Hmm?" Karin blinked.
"S-so..n-no com-comments abo-about m-me...liking y-you?" Toshiro worried.
"I don't have any" Karin shrugged, "I mean, I thought it was obvious".
"What was obvious?" Toshiro asked.
Karin stepped forward and kissed him.
"...Oh".