I'm getting more suspicious of gyaru each time she makes an appearance now. Surprised no one is saying anything, but remember that she's the first one who got Ichikawa's number, she also held his hand, and just maaaaaaybe it's a coincidence that keychain went missing and just so happen to appear when she comes along? Also notice how she notices Ichikawa looking at his own on the first page and her noticing it? Sneaky jealousy maybe? I don't know, just throwing some ideas out there.