Seo

Seo (先生, Seo) is a mystery; he appears to Arata Hinohara out of nowhere to offer advice and disappears shortly after.

Personality
Seo has a friendly attitude and acts kindly to Hinohara. Seo does not take things too seriously and isn't one to become frightened easily.

Gatoya Arc
Arata Hinohara in a fit of rage towards Tsukuyo while unable to find the missing Kotoha, is confronted by Seo a falsely convicted criminal.

He listens to Arata's problem and his quest to save the Princess, Kikuri and questions why he took such a job, and guides him towards Kotoha, by telling him to take full awearness of his seroundings and then disapears when Arata looks back.

Trivia

 * When translated from kanji, Seo (先生) means Sensei.
 * Second Character to know about Arata's quest