Chon-bean is a name Motomiya Mao came up with. His face is red, and it is expensive, 2000 yen ($20). And apparently, it can make your wish come true.
In chapter 10 when Mao and Hiro were on a "date", Hiro spotted a weird looking item. Hiro notices that Mao likes that weird looking keychain, and buys it for her. When they eat gyuudon in a restaurant, Mao opens up the package with the chon-bean and puts it on her cellphone.