The Girl I Saved on the Train Turned Out to Be My Childhood Friend, Vol. 8 (manga) - Fly Kennoji - Bog

The school trip has just started, and Hina's already snuck into Ryou's room! She's coming on strong, but how will he respond? Plus, Hina's not the only one trying to make a move-the next day is Torigoe and Ryou's souvenir shopping date! Though, when Hina accidentally sees them getting along, she takes a hit to her resolve that might be tough to recover from...