Myōga is a yōkai-flea who appears randomly and gives the han'yō InuYasha information on current events, foes, and the shards of the Shikon no Tama (Jewel of the Four Souls). Myōga is an old friend of InuYasha's father, and was originally charged with guarding InuYasha's father's tomb. But when Sesshōmaru came to it in order to look for the Tessaiga he fled and met up with InuYasha and Kagome. When he is not with the group, he is usually off gathering new information that can be useful. Otherwise, he is with Tōtōsai.

Myōga often flees before or during a battle, which often annoys InuYasha and the rest of the group. It becomes something of a running gag among the group that if Myōga is around, they must not be in danger.

Later on, InuYasha and the gang encounter old lady Shōga, Myōga's fiancé. Shōga controls the gang separately to catch Myōga as Myōga tries to run away from her. In the end, they were going to marry in the village that they were in, but Myōga flees and Shōga swears to find him, then marry him.

Myōga has an uncanny resemblance to another infamous Takahashi character, that being Happosai from Ranma ½, he also possesses some of Happosai's perverted tendencies. In the English version of the series, Happosai is portrayed by the same voice actor, Paul Dobson.