The grubby founder of Kyokujūji Sei Ken. Ruìyīng was at first the most promising student of Hokuto Ryūka Ken of his generation, but left after becoming disgruntled because he considered all other practitioners of it to be too weak. Upon leaving he asked his Hokuto Ryūka Ken master for the right to challenge Hokuto Shin Ken in order to become the strongest Hokuto Master but was refused. He then fought his own master but was hit with a poisoned arrow in the leg during the process, which he then chopped off. Wèi Ruìyīng later fought Tesshin Kasumi, Kenshirō Kasumi's father and the 61st successor of Hokuto Shin Ken, to a draw. It has been 30 years since he has been last sighted.
Ruìyīng is referenced again on the subject of Liu Zong-Wu. When confronted with an attack from the young Zongwu, Ruìyīng considered him to be above even his level when he was Zong-wu's age.