Imōto wa Shitte Iru

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Imōto wa Shitte Iru
First tankōbon volume cover
妹は知っている
GenreComedy[1]
Manga
Written byMari Gangi
Published byKodansha
ImprintYoung Magazine KC Special
MagazineWeekly Young Magazine
Original runNovember 25, 2024 – present
Volumes3

Imōto wa Shitte Iru (妹は知っている; lit. 'My Little Sister Knows') is a Japanese manga series written and illustrated by Mari Gangi. It began serialization in Kodansha's Weekly Young Magazine in November 2024, and has been compiled into three volumes as of August 2025.

Plot

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The series follows Kiichirō Miki, a salaryman who lives with his younger sister Miki. Despite having a boring personality in real life, he is secretly Fruit Parfait, a radio listener known for frequently sending detailed postcards to the program All Night Nippon. However, only Miki is aware of his secret identity.

Characters

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Kiichirō Miki (三木 貴一郎, Miki Kiichirō)
A 26-year-old salaryman who works as a system engineer. His alternate persona as Fruit Parfait is well-known among radio listeners, although only his younger sister Miki is aware of his identity. He was born Kiichirō Makabe (真壁 貴一郎, Makabe Kiichirō), but adopted his mother's maiden family name Miki after she divorced their father. He became closer to Miki after appearing with her in a variety show, substituting for one of Miki's idol groupmates. He cares deeply for Miki, to the point he gets angry when others criticize her.
Miki Miki (三木 美貴)
Kiichirō's younger sister and a member of the idol group xoxo (pronounced "Kiss Kiss"). She is known for her cold personality, but she cares deeply about Kiichirō, to the point she can even see his true emotions. She often appears in variety shows, particularly after her appearance with Kiichirō. She was born Miki Makabe (三木 美貴, Makabe Miki); despite the initial hesitation of her mother as it would mean Miki would have the same first and last name, she decided to adopt the surname Miki after their parents' divorce.
Sumine Hirose (広瀬 澄音, Hirose Sumine)
Kiichirō's co-worker and friend, who is popular among their male co-workers. She previously had a boyfriend, but they broke up following an argument.
Tsubomi Yokō (横尾 蕾, Yokō Tsubomi)
Kiichirō's co-worker and an accounting manager. As she is 34 years old, others jokingly refer to her as an "old lady". Like Kiichirō, she is an avid radio listener and also often sends postcard to programs, although she has not had any success in being acknowledged on-air. She is initially unfamiliar with Kiichirō's identity as Fruit Parfait, although she later finds out after a certain incident.
Akari (あかり)
An idol who belongs to the same group as Miki. She was supposed to appear on the same variety program as Miki, but because she was unavailable, Kiichirō substituted for her at the last minute.

Publication

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The series is written and illustrated by Mari Gangi. It began serialization in Kodansha's Weekly Young Magazine on November 25, 2024.[1] Gangi created the series as they found the concept of "postcard craftsmen", people who create detailed postcards to send to radio programs, interesting. She originally aimed for the Miki siblings to have a more cheerful personality, but changed them to have a more reserved personality at the suggestion of her editor.[2] The first tankōbon volume was released on March 6, 2025;[3][4] three volumes have been released as of August 2025.[5]

No. Release date ISBN
1 March 6, 2025[4]978-4-06-538788-7
2 June 6, 2025[6]978-4-06-539948-4
3 August 6, 2025[5]978-4-06-540537-6
4 October 6, 2025[7]978-4-06-541138-4

Reception

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The series was nominated for the 2025 Next Manga Award in the print category, and was ranked thirteenth.[8][9]

The series received attention online for its discussion on postcard craftsmen, with a tweet promoting the series getting over 50,000 likes on Twitter.[2] Volume one received a reprint a few days after release due to high demand.[10]

References

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  1. ^ a b "うちのお兄ちゃんは世界で一番面白い、兄妹コメディ「妹は知っている」ヤンマガ新連載". Natalie (website) (in Japanese). Natasha, Inc. November 25, 2024. Retrieved September 17, 2025.
  2. ^ a b "テレビに辟易した若者たちが「ラジオ」に熱中している…SNS「5万いいね」を集めたマンガ『妹は知っている』が「ハガキ職人」を主人公にしたワケ（ヤングマガジン編集部）". Gendai Business (in Japanese). Kodansha. June 16, 2025. pp. 1, 3. Retrieved September 17, 2025.
  3. ^ "皆につまらないと思われている兄と、そんな兄の本当の姿を知る妹のコメディ1巻". Natalie (website) (in Japanese). Natasha, Inc. March 6, 2025. Retrieved September 17, 2025.
  4. ^ a b "妹は知っている（１）" (in Japanese). Kodansha. Retrieved September 17, 2025.
  5. ^ a b "妹は知っている（３）" (in Japanese). Kodansha. Retrieved September 17, 2025.
  6. ^ "妹は知っている（２）" (in Japanese). Kodansha. Retrieved September 17, 2025.
  7. ^ "妹は知っている（４）" (in Japanese). Kodansha. Retrieved September 17, 2025.
  8. ^ 「次にくるマンガ大賞 2025」投票受付スタート！ エントリー総数9,432作品の中からノミネート100作品が決定. Da Vinci News (in Japanese). Kadokawa Corporation. June 20, 2025. Retrieved September 17, 2025.
  9. ^ コミックス部門 結果発表 - 次にくるマンガ大賞 2025. Tsugimanga (in Japanese). Retrieved September 18, 2025.
  10. ^ ふんわり兄妹コメディ「妹は知っている」1巻、好評を受けて大増刷決定！. Manga Watch (in Japanese). March 11, 2025. Retrieved September 17, 2025.
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