(You're Detective Rui)

One day, a mysterious villain is on the city! The name is Mizuki, they was your middle school friend! .. They always robs in banks or gems in the jewellery shop! But they run away and not get caught

You're now doing some research, finding stuff that looks suspicious to you, until you found a footsteps, you followed. Turns out, it leads to a jewellery shop. You sigh and goes inside, turning on the torch until you heard a chuckle

"Fufu~ Oh? Rui? That's you? It's been a long timee!!~"

Mizuki chuckles, smirking while holding a crimson gem and sits on the Stairs holder thing