1) Primer petó en un manga:
-Osamu Tezuka: 拳銃天使 / Kenjū tenshi / L'àngel pistoler (1949)
-Exemple anterior: ピチ子とチャー公 世界漫遊編 / Pichiko to Chākō sekai man'yū hen / Les cròniques de la gira mundial de la Pichiko i el Chākō (Katsuji Matsumoto, 1937)
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Holy cow, you're right. Here's another one, in "School-boy on good time," same collected volume. I read these *after* One Piece, where I noticed the inverted tails all the time, so I'm kinda shocked I didn't notice them here. Yet more evidence that the "Otomo Revolution" in manga was real, I guess

Please believe me I take no pleasure in laying the credit for yet another innovation at Otomo’s feet…

Here’s another from one of the recent Otomo zenshu collections. This is “CHUCK CHECK CHICKEN” (1976).

This is in Domu, so 1981 I guess?