いやあ… いつの間にかすごい人になっちゃったんだなあ。 僕の知ってる鴫野は いわゆる オタクっていうか一人で ずっと ゲームやってるような奴だったのに。
Isn't ちゃった used for regrets?
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Sign up to join this communityちゃった is a contracted form of -てしまった. This しまう (仕舞う in kanji) originally means "to end (up)". See this entry on jisho. Just like "to end up" in English does not always imply an undesirable outcome, Japanese ちゃう/てしまう does not always express the sense of regret. Here, すごい人になっちゃった just means "he ended up becoming a great person" or "he turned out to be a great guy".
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