not but (だけでなく): He is not but a friend, but also a mentor. (彼は友達だけでなく、メンターでもあります) - 試験に出る! 英単語検索辞書

not but (だけでなく): He is not but a friend, but also a mentor. (彼は友達だけでなく、メンターでもあります)

He is not but a friend, but also a mentor.