Note: In this particular situation OTP implies "most preferred pairing" rather then "pairing one believes is meant to be together". I take issue with the latter because there is a difference between believing two characters are meant to be together and using canon evidence to support the idea that two characters are meant to be together.
a.73 ~ OTP
"I like this cafe, the atmosphere, the sweets... not to mention the service." Karin tugged on Toshiro's sleeve as his cheeks flushed. The young teen finally found the confidence to ask her out and the quaint cafe was the place she picked. The flush color on his cheeks changed to paleness upon seeing the person behind the counter. "I'll order."
"I want to pay for the first date Toshiro."
The boy glanced nervously at the silver haired man. Karin seemed quite fine with him and soon came back with a couple of coffees as well as some sweets. A frown was on her face. "Karin... can I ask... what kind of feeling do you get off that man?"
The female swallowed. "You usually avoid asking what I pick up with my empathy." She sighed. "Normally the vibe I get off Ichimaru-kun is nice and I feel safe around him. He's honestly part of the nice atmosphere. Today though..."
"Animosity..." Toshiro saw the man open one pale teal eye and look at him, a smirk of a different kind on his face.
"Toshiro... why would your father have any kind of animosity towards you." Karin watched as he flinched from surprise. "He is your father, right? I mean... that's the kind of feeling I'm getting off him, the feeling a parent feels for their child."
Toshiro glanced at the man, realizing that Gin's posturing was changed, as if a mask had dropped. He thought it had something to do with needing to keep the job. Shaking his head he turned back and began to enjoy the items Karin picked out. A desert item with two straws was suddenly placed on the table and he felt the man lean over his shoulder and whisper. "Does Ran-chan know?"
The corner of his mouth twitched. "Yes tou-chan... ka-chan knows."
Gin flinched while Karin stared. The man continued to whisper. "Shiro-chan, you're not supposed to remember that anymore then..." The man paused, watching the confused look on his face. "You don't remember."
Toshiro's face paled. "I thought the reason Karin picked up on... well, that... was because... well, you thought of Matsumoto, you and I as a family unit. Not because..." The boy looked away. "... we actuallly are."
Gin looked at the girl, his eyes revealing his surprise. The man stood up. "I'd like to explain things to you Shiro-chan, but you know I'm hiding here in the living world."
"I won't say anything." Toshiro's voice strained.
"It's not something I can explain in one visit." The man looked at Karin and patted Toshiro's shoulder. "You have a nice girlfriend. Please... don't make the mistakes we did with you."
"What is..." Gin however slipped away.
"Your father is nice."
"To my mother and myself. He's..." The boy looked at the treat. "What did he mean by that?"
"I have an idea and will explain it later."
"Yes, but..." Toshiro turned to see Gin give him a thumbs up and a sad smile.