Everyone and their mother may know he loves Kasahara, but he hides it pretty fucking well from her. Even telling her she's useless and that she should quit.
And when Kasahara was in danger, he was all like "oh god I shouldn't have told her all these horrible things, it all my fault. Please be safe !" . And when he finds again, all he has to say is "Well, I guess you did pretty well this time. You should still quit though"
Sounds pretty fucking tsundere to me.