Gonna be a contrarian and speculate that rather than joining the Paisen Bowl, Opai Senpai is going to berate him for being timid and not recruiting new members. From there Nagatoro gets jealous/pissed and jump out to defend him/her territory. Cue training/cultural festival arc where gyaru harem bands together to show up Opai Senpai.
So she wants to play "whack the sempai" and "pop up sempai". Her intentions are way too easy to read at this point. Just grab his gun and have some fun.
Distinguishing people by their footsteps is surprisingly easy. If you are familiar with them for some time (very few months, sometimes even weeks), you get the hang of it, if you want it or not.
@flavorful: +1 Funny. Sadly their is no upvote system.