The hero can only top Ash and Lyric. If you go home and head up to the MC's bedroom after beating the slime dungeon, you can choose to sleep by interacting with the bed. Then, the scene between Ash and the Warlock happens and Ash teleports directly to MC's room. There you can choose to be the bottom or top for him, but you can't avoid it if you go down this route. Then the MC can only top Ash or Lyric while waiting to leave the Faerie Realm. Otherwise, every sexual interaction has the MC as the bottom.