尾根山 厳太

He has the name and appearance of Oneyama Genta from PurexCure. Despite that, these characters are two different people because PurexCure and Koibumi Romantica are set in different times. (Koibumi Romantica's events are happening at least 50 years before the events in PurexCure.)

He seems to be the martial master of Tsukumo in Astraythem because he called him "Master".