He would definitely threaten Tengen to stay away from her, and then he would threaten him again to make him stay quiet about it.
Another random thought
Would Tengen try to take fem Genya on the Entertainment district mission?
I see it going one of two ways
1: Tengen trying to but getting stopped by Kanao, the butterfly girls and the boys (and getting beaten up by Sanemi for it later)
2: him knowing she’s Sanemi’s sister and not doing it because he doesn’t have a death wish
What do you think?
I feel like tengen would absolutely do it and for a couple reasons.
1. Sanemi has insistently denounced Genya as his sister, explicitly stated by Mitsuri in season 3, with that, and with there allegedly being no blood or emotional connection, Tengen would not see taking Genya as a risk to his bodily safety.
2. Tengen is extremely confidant in himself, he’s a well honed warrior, in a 1V1, I do think Sanemi would beat Tengen, but Tengen would still be able to hold his own pretty well at his prime and also he wouldn’t explicitly know what he is going up against when it comes to Sanemi methinks.
3. Tengen also explicitly states he cares more about his wives first thing first than anything else, he even orders them to prioritize themselves over anything else if it comes down to it. We can see when he’s alone and in brief moments he’s scared and worried for their safety, even if he did have some concern for how Sanemi might react, he would still think “I’ll deal with the consequences later” because his wives are the only thing he truly cares about.
That’s not to say Tengen wouldn’t care about the well being of Genya, he did with the kamaboko squad, but still, not nearly to the same extent.
Now for how Sanemi would react I struggle with coming to a conclusion because.
1. He has again completely denounced the notion of having a sister, and to maintain this he has to appear as unbothered by what happens to Genya or what missions he goes on.
2. To do that he can’t blow his top and possibly have some rumors of his reaction get back to her and give her hope
3. It’s also corps illegal to fight members lmfao.
But Sanemi is still Sanemi, he is protective, he is worried. He is scared, his baby sister went up against (technically) two uppermoons and the RLD district is completely gone and pretty much everyone almost died.
So I think there would be a confrontation between Sanemi & Tengen, but probably not much of a physical one, I think his main priority would be seeing Genya for himself and making sure she is more or less okay, like how he went and checked up on Genya after S3 in the light novels.
This stuff is so fun to think about!!! Thank you for the ask!!!!