Ore no Imouto ga Konnani Kawaii Wake ga Nai.

Synopsis

Feeling frustrated that Kirino is ignoring her in favour of a popular mobile game called Love Touch that lets you exchange texts with virtual girls, Ayase asks Kyosuke to do something about it. After Kyosuke brings it up to Kirino, she gives him Love Touch to avoid being tempted by it, only for Kyosuke to end up becoming addicted himself. As Ayase becomes angered upon learning of this from Manami, Kyosuke attempts to explain how the game's heroine is similar to Ayase. He suggests imitating the heroine to better hold Kirino's interest, but this is soon met with violent backlash from Ayase when dubious phrases are brought up. After Ayase goes to Manami for advice, Kyosuke is shown the error of his ways when Ayase decides to imitate the game's yandere route in front of Kirino.

(Source: Wikipedia)