Deku calls Bakugo “Kacchan” because it’s a childhood nickname formed from Bakugo’s first name, Katsuki, and it reflects their long, complicated bond rather than just being a casual pet name. The name sticks even after their relationship turns from one‑sided admiration and bullying into a rivalry built on grudging respect.

Meaning of “Kacchan”

  • “Kacchan” comes from “Katsu” (from Katsuki) plus the affectionate Japanese suffix “‑chan,” often used for kids or close friends.
  • Deku started using it when they were little, so for him it’s tied to childhood memories, admiration, and the idea that Bakugo was someone he looked up to as a hero figure.

What it says about their relationship

  • The nickname shows how Deku still sees Bakugo as that same person from their past, even after years of bullying and conflict, which makes their interactions more emotionally intense.
  • Bakugo letting Deku keep using “Kacchan” suggests he acknowledges their shared history and, over time, accepts Deku more as an equal, even if he never admits it openly.

Why Bakugo allows it

  • In early years, Bakugo saw Deku as beneath him, so he didn’t bother correcting the nickname because Deku’s opinion didn’t matter to him.
  • As Deku grows stronger with One For All, the nickname becomes a reminder of how far they’ve both come, fueling Bakugo’s drive to surpass him while still keeping that thread of familiarity.

TL;DR: Deku calls Bakugo “Kacchan” because it’s an affectionate childhood nickname from “Katsuki,” and it stayed with them as a symbol of their deep, messy mix of nostalgia, rivalry, and respect.

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