You mean when & why I start to think Izumi is somehow related to the old man?
Actually it's not really mentioned in the game, instincts told me that...
I'm already having a little suspect when Izumi disappears day after day, added to Souma saying he's wearing designer clothing head to toe...when Yuki called the lawyer and he mentioned a Tsukihara-san whose voice sounded awful young, I'm pretty sure about this. That's definitely a main character, and the most suspectable person is Izumi.
But maybe that's Korean or Chinese TV dramas affected me too much...you know, they're always full of this kind of things...often the male protagonist (very rich) deep in love with the female protagonist (not so rich or just poor) and his family doing all sort of things to part them....So I always get a strange feeling when playing XD
(because idk if the reason that old Tsukihara targeted Yuki is about Izumi or not..if not that will be embarrassing lol)