Height 175cm (5'7") A reliable university student who wants to become a civil servant. Works part-time under Richard. Like his name, he's straightforward until he encounters an unusual situation - then he becomes a heedless "ally of justice" ('seigi no mikata' in Japanese). As a child, his parents were divorced with his mother taking custody of him; he then lived with his maternal grandmother. His maternal grandmother was also a single mother who stole to make a living. One of the items she stole was a pink sapphire engagement ring, which she thought the loss of led to the death of the woman who it belonged to. In her guilt, she kept it until her death where she bequeathed it to Seigi. Seigi's quest to return the ring to its rightful owner marks the beginning of his association with Richard de Vulpian. Novel spoilers

Spoiler

In the novel, there are moments where Richard and Seigi seemingly flirt with each other and are often mistaken as a romantic couple by others. Their relationship is very close as they are able to say how much they like each other in both the anime and novel, however, it is unknown whether they mean it romantically or platonically.