I guess feigning you are surprised does actually work with Kogasa.
I believe it's actually been described canonically to at least be able to fool her. Whether or not feigning actually sustains her I think is up to interpretation.
Maybe you're cold because you're exposing your armpits and belly button and stuff?My training is truly outstanding, isn't it? Hooo ho ho!♡How's that!?The temperature's dropped, and it's especially cold today...Hot-blooded...How do you like that!?Withstanding cold is also vital training!!! I...I did it! Now that I could surprise Reimu, I'm invincible!Yes, yes, yes. What a pain!SmugW-...well, anyway, don't just stand around talking, come inside!The results of my training! A full-power Be Surprised!Wowww, you sure surprised me. (woodenly)...power!
