Is Imōto wa Shitteiru Finished? No — Still Ongoing, 9 Volumes
No — Imōto wa Shitteiru is not finished yet (still ongoing). 9 volumes are out in Japan; the latest came out in October 2026.
Everything below reflects the Japanese edition — the source of truth that runs months or years ahead of English releases — computed from official publication records.
Volumes in Japan: 9 (latest: 妹は知っている（9）, 2026-10-06)
Next volume in Japan: not yet announced in Japan.
Status: No — Imōto wa Shitteiru is not finished yet (still ongoing). 9 volumes are out in Japan; the latest came out in October 2026.
Serialized since: 2025
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