Beatiful young lady saw great detective! Case of murdered teacher - S1.E30

Yukiji is found murdered at a hot spring inn and Detective Nagi decides to take it upon herself to solve the mystery. After a number of wrong assumptions, Nagi blames the voice in the sky ("Ten no Koe", i.e. the narrator). Kirika sends another butler to defeat Hayate, and they have a B-Daman battle.