The fact that he chased after her and said point blank to her face that she's the "most stimulating" to him is amazing. This is someone who's seen as spineless and cowardly to the point of isolation. Now that they've come this far, to say something so honest, it's more meaningful than saying "I love you". He's confessing to her the only way he knows how. Not to mention the sexual connotation of the word "stimulating".
wow, 'stimulating' what a fine word he's chosen there.
I think it really is the best word since we're talking about sexiness and nagatoro is losing confidence here, so who's more stimulating to him is what matters, to boost her confidence, lol.
Well, you know what they say: drop by drop the glass gets filled. So nagatoro is just few steosnaway from fully falling for senpai...if she isn't already.