Momoko Touyoko

Momoko is Yumi's friend, and a high school first year student. She has a lacking presence, and is often ignored by her friends despite her efforts to gain attention; as such, she soon gave up on building relationships with other people. After a match through LAN mahjong, Yumi acknowledges Momoko's skills and finds her; the two become friends afterwards. Her mahjong playing ability comes when she augments her negative presence into an advantageous stealth state, causing her opponents to miss her moves.

(Source: Wikipedia)