Short answer: Atsu is 28 years old at the start of Ghost of Yōtei.

How the timeline sets Atsu at 28

The story establishes two fixed points: Atsu was 12 when the Yōtei Six destroyed her family, and she returns to Ezo sixteen years later to begin her hunt. That puts her at 28 during the opening chapter (12 + 16).

Why you may see 28–29 (or 28–30) elsewhere

In-game materials peg her in the “late twenties,” with a wanted notice listing 28–29. Community compendiums often round that to 28–30 to cover the span across the game’s events. In practical terms, she’s 28 at the outset and remains in her late twenties throughout.

Actor vs. character age

Erika Ishii performs Atsu and is older than the character. That’s normal in performance capture and voice work; an actor’s age doesn’t need to match the role as long as the look and delivery align with the character.

Why Atsu might read older on screen

Her design leans into a weathered, battle-worn look that fits a mercenary shaped by years of hardship. In a 1603 setting defined by war’s aftermath, that visual language can easily read as “older” even when the character is in her late twenties.

Quick reference

Clue What it states Resulting age
Story timeline 12 at the tragedy; returns 16 years later 28 (start of the game)
Wanted notice Lists her in the late twenties 28–29
Community summaries Broaden the range across events 28–30

If you’re just looking for a single number, 28 is the canon starting point. The small ranges you’ll see elsewhere simply reflect how the game frames her as being in her late twenties throughout.