Chabahara

The two have a quite a few interactions in canon material up until Tenko's death in Chapter 3. Their first interaction is when Shuichi was introducing Kaede to Tenko and Tenko accused him of being a 'Degenerate Male' despite him not doing anything. They have similar interactions with Shuichi trying to talk to Tenko and Tenko mostly attacking him for being a male no matter what.

After Kaede's death in Chapter 1, we see Shuichi become the new protagonist and as he enters the dining room saying hello to everyone they all seemed shocked to see Shuichi finally come out of his room and to see him without a hat. Kokichi made a remark talking about how Shuichi doesn't seem as emo anymore without his hat because of him losing Kaede to which Tenko responds lecturing Kokichi saying that Shuichi is strong for overcoming Kaede's death and that Kokichi just needs to shut up.

There's also a bonus mode in Chapter 2 where Tenko, Angie, Kirumi, K1-B0, Himiko, and Shuichi all go to the pool and Tenko tells Shuichi that she wants to feel like a celebrity to which Shuichi asks if she want's to go swimming and she admits that she can't swim very well. Kirumi then enters and asks the girls to go change so that she can help massage them and set up the swimming pool and then Tenko tells Shuichi that she'd be delighted if he wanted to sneak a peak into the girls locker room while they're changing so that she can have an excuse to put a degenerate male in his place. Shuichi then deny's that he'll ever do that and Tenko nods roughly indicating that she trusts him.

In Tenko's love hotel event Shuichi enters the suite and he himself questions what Tenko's fantasy would be like since she hates a ton of men. Tenko then tells Shuichi to do "It" Shuichi is confused and then asks what she means and Tenko explains that they made a bet and if Tenko lost then Shuichi could use her however he'd like to. And if Shuichi lost then she could do whatever she wanted to him. But she then follows up saying that she knew she wouldn't win so she made the bet on purpose in order to get Shuichi's love. She then admits that she's confused as to why Shuichi isn't doing anything to her yet but her body was ready. Shuichi then tries his best to tell Tenko that he doesn't want to do anything rough with her and then Tenko tells him "Ooohh! So wonderful! I knew you'd say that, Brother Shuichi! You're nothing like those other degenerate males that only fantasize about making love to girls!" Shuichi then continues to tell her that he doesn't want to do anything to her and by doing anything he can technically do nothing. Tenko then says that she respects Shuichi for being humble but then get's angry calling him an "Insensitive Degenerate Male" for not wanting to do anything to her. She then admits that she loves him and made a bet with him just for that reason. She then finally yells out her feelings and says that she'll continue to love him no matter what and that she wants to be his and his alone. In the end she says that she'll always be ready for Shuichi no matter what, any time in any place she'll be ready. And they depart on fairly good terms.