In Japan, from your second playthrough and up, you can join clubs by talking to the girl near the right side of the school courtyard.

Joining clubs can give you a small boost to your stats, exclusive items, and change certain dialogue.

If your Stand is Ocean Blue, The Joykiller, Mr. Big, Specials, Pharoah Sanders, or Adam Ant, your occupation in the post-credits scene may change depending on the club you joined.

Club Benefit Notes
Sports
Baseball The attack item "Baseball Bat" will be added to your inventory.
Soccer HP +1
Tennis Speed +1
Basketball Speed +1
Volleyball Speed +1
Table Tennis Speed +1
Swimming HP +1 Changes certain lines of dialogue.
Track HP +1
Boxing Power +1
Kendo Power +1 Changes certain lines of dialogue.
Judo HP +1 Changes the Small-Time Criminal event in Singapore.
Karate Power +1
Sumo HP +1 Male only. Changes certain lines of dialogue.
Archery The attack item "Bow and Arrow" will be added to your inventory. Female only.
Gymnastics Speed +1
Cheerleading SP +1, and you will also learn the move "Anthem".
Liberal Arts
Art Club Spirit +1 Changes certain lines of dialogue.
Drama Club SP +1 Increases the probability of equipping the Bunny Suit from 10% to 50%.
AV Club Durability +1
Tea Ceremony Club Spirit +1 Changes certain lines of dialogue.
Calligraphy Spirit +1
Book Club SP +1 Changes certain lines of dialogue.
Handicraft Club Durability +1 Changes certain lines of dialogue. Adds a hotel event and gives you an additional option for the Littering event in Singapore.
Cooking Club SP +1 Changes certain lines of dialogue.
Science Club Spirit +1 Changes certain lines of dialogue.
Chorus Spirit +1
Brass Band HP +1
Modern Music Club Power +1 If your Stand is Sonic Youth, and you answer Yes when the girl asks you if you play the guitar, you will learn Punk Rock and Death Metal.
School Paper Durability +1
Photography Durability +1 or randomly SP +1 and the attack item "Baseball Bat" will be added to your inventory. You will get additional dialogue if you have the Jotaro fan trait (this dialogue will however not occur if you received the baseball bat).
Shogi Spirit +1
Other
Manga Club None
Occult Club None Changes certain lines of dialogue.
Film Club None
Game Research None Changes certain lines of dialogue.
Computer Club None
Train Club None Changes certain lines of dialogue.
Volunteer Club -1 Bad Karma


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