柳生比呂氏 nicknamed 「Gentleman」

柳生比呂氏 is nicknamed 「Gentleman」 or 紳士。And it was explained this in the 学プリ: 柳生の告白 why he is called that. He's a golf player, and was originally in the golf club before being recruited by 仁王雅治 to join the tennis club. 柳生 said that golf is the only sport that doesn't require a ref and is depended on the men to judge themselves on the field. Something about honesty and integrity; therefore, golf is a gentlemen sport.

Somehow he uses a golf swing on one of his tennis moves which the ball turns into to a beam and kills the opponent. I dunno, but 海堂 was able to do this move in one of the matches I saw. Too bad his partner 乾 sucks dick and they loose the match.

I noticed there are a lot of nicknames for the players:

柳生比呂氏: Gentleman or 紳士
真田弦一郎： 王帝 (King)
仁王雅治: プリテン者 (Pretender)
橘桔平: 獅子 (Lion)
千石清純: ラッキ千石 (Lucky Sengoku)
跡部敬吾: 氷帝 (Ice Emperor)
忍足侑士 & 不二周助: 天才 海堂 薫: マムシ (Snake)
菊丸英二 & 大石秀一郎: Golden Pair
越前リューマ： テニスの王子様!!! (Prince of Tennis!)