Idk, I can see him forgiving Hasegawa that easily because he suspected her of just trying to use him in the first place and never actually considered her wanting to be friends. Kind of like a Nothing gained - nothing lost mentality.
Definitely thought Hasegawa was gonna ask Houjou to get info about Rei out of Tohno. Causing Tohno to jump to the conclusion that Houjou really is just trying to get closer to Rei through Tohno.
At least I was hoping that it would play out like that. I want to see Tohno's suspicions at least...