Furude Rika

Rika is a grade lower than Keiichi, and thus is a classmate of Satoko's.

She is very quiet and reserved for her age, which makes her almost the polar opposite of Satoko. However, the two of them can often be found in each other's company.

Whenever Satoko is in tears after losing against Keiichi, it is Rika who cheers her up. When Satoko wins, Rika comforts Keiichi instead. When Keiichi teases Rena, Rika comforts her.

In fact, Rika comforts whomever is in need of comfort.

She seems happy with it.

Spoiler

When by herself or with Hanyuu, Rika completely drops her cutesy and child-like personality and displays a much more cynical, mature, apathetic, serious and occasionally hostile personality, developed as a result of her 100 years of traveling through the Sea of Fragments.