this character only appears in tekken 4, as a alternate costume for Ling Xiaoyu, she has her own voice, is an high pitch voice.
Miharu is a student in Mishima High School/ Mishima Polytechnical School,
she is a close friend of Xiaoyu,
she practices and possible learned from Xiaoyu Chinese Martial arts,
she is not very good at school.
this is a very strange case, in tekken 4 several fighters were removed, but they had time to introduce a totally new character, and them never use her again, possibly because of the resemble to Asuka, but they could at least make her appear in some sort of cameo in endings, even in the new Tekken movie Blood Vengeance that stars Ling Xiaoyu her best friend as the main character.
Miharu could appear in Tekken Tag 2 as a full alternate character costume for Xiaoyu, with her own voice, her own intro and win animation poses.