Matou Zouken in his youth. He came up with the family name Matou as wordplay for his original given name, as the second kanji in Matou (間桐) can also be read as kiri.
His younger design first appeared in the hanafuda game for Fate/hollow ataraxia and was featured in flashbacks in the Fate/Zero anime adaptation. He later briefly appeared in the London chapter of Fate/Grand Order, with an even younger version appearing in the Paper Moon chapter.
