OVA 9
"But I can't stop. Puberty and dirty jokes! I just can't give them up!"
"And I can't seem to give up being your straight man. But just give it a rest for today please."
Not to spoil the whole scene, I'll leave it at that.
There are SO MANY hints (more like clue bats to the back of the head). Tsuda meets Shino's mother off screen. To paraphrase "a great step was taken that day." Shino still wears the necklace from Tsuka from the Christmas party. Shino was the only one to talk to Tsuda's mother, on the phone. Kotomi has acted as Shino's "spy" on more than one occasion. The phone call when he was on the class trip, and Shino got lonely. It's all right there. I'm still confused why people are so into "shipping," when the logical conclusion has been confirmed many times.
And remember, Hikasa Youko has NEVER lost the harem wars. Poor Hanazawa Kana. I don't think she's ever won.