Gotten all warped from playing video games with 〜じゃう

さっちゃん:

「歪(ゆが)みすぎだよ！」

“You're way too twisted!”

「琴(こと)ちゃんゲームばっかりやってるからそんな風(ふう)に歪(ゆが)んじゃうんでしょ！」

“It's 'cause you only ever play video games, Koto-chan, that's why you've gotten all warped like that!”

Key Points

1. 歪(ゆが)んじゃう = end up getting warped

   • 歪(ゆが)んじゃう is casual speech for 歪(ゆが)んでしまう, from 歪(ゆが)む “to warp, twist, distort” plus 〜でしまう.

2. Why じゃう follows ん

   • For verbs whose て-form ends in で, 〜でしまう contracts to 〜じゃう in casual speech.

   • 歪(ゆが)む becomes 歪(ゆが)んで, then 歪(ゆが)んでしまう becomes 歪(ゆが)んじゃう.

3. ゲームばっかりやってるから gives the blamed cause

   • ばっかり is a casual form of ばかり, meaning “nothing but” or “all the time”.

   • ゲームばっかりやってるから means “because you do nothing but play games”, setting up Sacchan’s explanation for why Kotoha acts the way she does.

4. そんな風(ふう)に points to Kotoha’s attitude

   • そんな風(ふう)に means “like that” or “in that way”, referring back to Kotoha stepping on Sacchan’s head.

   • The phrase makes 歪(ゆが)んじゃう describe the way Kotoha has supposedly turned out, not a single action she just performed.

5. んでしょ makes it an accusation

   • The ending んでしょ is casual のだろう, used here to press Sacchan’s conclusion onto Kotoha: “that’s why, right?”