Ogawa Kentarou

Profile
He first appears along with Miki, joining one of the Houses.

During the events of Sengoku Rance, he was heavily wounded by the acolyte Seiryuu and become a demon when Miki gives him her blood to save him. (Updating in progress)

(Note: profile seems to document his appearance in Sengoku Rance, which is not his first appearance or mention in the series. Suggested change:

"Ogawa Kentarou is a human from Japan of the Dimension 3E2 (Japan of modern day Earth, not to be confused with JAPAN in Rance World). He is childhood friends with Kurisu Miki (Little Princess), but is ignorant of her romantic interests in him. Miki turns him into a demon in the events of Sengoku Rance.

He is the weilder of the Holy Sword Nikkou.")

Rance 1
He is mentioned by Miki when you meet her in the castle.

Toushin Toshi 2
He only appears in the storyline.

Kichikuou Rance
He was severely hurt when running with Miki and Nikkou and they seek selter in Leazas's castle. This result in Kamiera leading a few other demons attack Leazas to get Miki back.

Sengoku Rance
He appears along with Miki, still looking for a way to stop her from becoming the Demon King. During the course of the game, he is mortally wounded by one of Xavier's Apostles. Miki saves his life by turning him into a demon, strengthening him in the process (permanently).