Suichi - he used to collect hats but now he likes pins/badges/patches (really anything small that can be attached to something) and puts them on jackets or bags.
Maki - seemingly nothing but she actually has a box in her closet full of soda tabs so she can one day make a chain.
Kaito - this man has a crow mentality. Anything shiny on the side of the road is automatically coming home with him unless someone (Maki) somehow stops him. He’ll never make it through a metal detector because there’s random change in his pockets 24/7.