source: [面白い事を喫茶店で発見した涼宮ハルヒのGIF画像｜無料GIF画像検索 GIFMAGAZINE 18490]

(of a person, action, or motive) lacking consideration for others; concerned chiefly with one's own personal profit or pleasure:

利己的な, 自己中心的な; わがままな(↔ unselfish, selfless); 〖it is selfish (of A) to do〗 (A〈人〉が)…するとはわがままだ

e.g. I joined them for selfish reasons.