Boku wa Imōto ni Koi o Suru

Boku wa Imōto ni Koi o Suru (僕は妹に恋をする) is manga series by Kotomi Aoki. Originally serialized in Shōjo Comic, the individual chapters were published in ten tankōbon volumes by Shogakukan from May 2003 until August 2005. The series focus on fraternal twins Yori and Iku, who fall in love with one another despite being siblings.

The manga series was adapted into a one-episode original video animation that was released in May 2005 and a live-action film starring Jun Matsumoto and Nana Eikura that premiered in Japan on January 20, 2007. A ten volume spin-off series focusing on Yori's upperclassmen Takuma Kakinouchi and his childhood sweetheart Mayu Taneda was serialized in Shōjo Comic from December 2005 through August 2008.

Characters

 * Yori Yuki (結城 頼)
 * Iku Yuki (結城 郁)
 * Haruka Yano (矢野 立芳)
 * Tomoka Kusunoki (楠 友華)
 * Saki Yuki (結城 咲)

Manga
Written and illustrated by Kotomi Aoki, Boku wa Imōto ni Koi o Suru were originally serialized in Japan in Shōjo Comic. The individual chapters were collected and published in ten tankōbon volumes by Shogakukan, with the first volume released May 26, 2003; the last volume was published on August 26, 2008. The series is licensed for regional language releases in France by Soleil Productions under the English title Secret Sweetheart, in Spain by Editorial Ivrea, and in Taiwan by Ever Glory Publishing. The original volumes were also imported to the United States and sold as is by Borders and Waldenbooks bookstores in early 2005. In March 2008, to celebrate its 40th anniversary, Shōjo Comic posted free chapters of Boku wa Imōto ni Koi o Suru on its website, along with a new side-story.

A spin-off series, Boku no Hatsukoi o Kimi ni Sasagu (僕の初恋をキミに捧ぐ), began serialization in Shōjo Comic simultaneously in 2005. Focusing on Yori's upperclassmen Takuma Kakinouchi and his childhood sweetheart Mayu Taneda, the series ran until mid-2008. Shogakukan published the individual chapters across twelve tankōbon volumes, with the first released December 20, 2005 and the last on August 26, 2008.

Original video animation
Boku wa Imōto ni Koi o Suru: Secret Sweethearts - Kono Koi wa Himitsu (僕は妹に恋をする シークレット・スウィートハート この恋はひみつ) is the original video animation (OVA) adaptation of the manga. On May 18, 2005, Shogakukan released a DVD for the original video animation. Directed by Mayumi Nishimoto, the hour-long, one episode OVA used the song "Ai ga Hoshii" (愛が欲しい) by Shion as its ending theme.

Live action film
The manga was adapted into a live action film by Toshiba Entertainment. The film was directed by Hiroshi Ando and produced by Shogakukan, Toshiba Entertainment, Zoom Enterprise and Nippon Television. It was released in Japan on January 20, 2007 and in Taiwan on June 1, 2007. The film features Jun Matsumoto as Yori Yuuki, Nana Eikura as Iku Yuuki, Ayaka Komatsu as Tomoka Kusunoki, Yuko Asano as Saki Yuuki and Yuta Hiraoka as Haruka Yano. The ending theme of the movie is "Kitto Eien ni" by Crystal Kay.

Reception
The first seven tankōbon volumes of Boku wa Imōto ni Koi o Suru sold 2.5 million copies by May 2006.

A reviewer for Manga News describes the first volume of the manga as "a mature shojo, appealing and rather captivating". A review of the second volume of the manga commends the author's art as "very pretty". It also comments on the incestuous relationship "Between those two brother and sister are sometimes pushed a bit too far and I found Yuki a bit too silly at times. But that also gives charm to the character." PlaneteBD's Faustine Lillaz comments on the manga's art which "barely save the day. The trait is fine and the style rather pure and the background details are rarely presents and when they are it's only to reinforce the forbidden aspect of Iku and Yori relationship (church, bedroom with parents outside)." Carlos Ross of T.H.E.M. Anime Reviews criticized the hour length of the OVA, feeling its compression of the original manga story causing Yori's feelings for his sister to seem "extremely abrupt and out of left field". Noting that the OVA adaptation departed from the usual "incest-taboo" set up, Ross considered the premise "Freudian" and "very unrealistic", stating "most of us don't need social taboos to think of bedding our siblings as being kinda gross: in psychology, it's called the Westermarck effect, where constant, early contact with a member of the opposite sex (related or not) leads to an aversion to sexual attraction". Ross also disliked the characterization of Yori, calling him a "raging, violent, jealous, abusive, creepy jerk", and the other characters as "over the top", detracting from the story. Though he found the animation itself average, Ross praised the background art as varying "from gorgeous to amazing". Anime News Network's Carlos Santos criticises the manga for its lack of depth. "'[Yori and Iku] basically spend each chapter getting dangerously close with each other, often in explicit ways, and this smut is repeated over and over until you just want to read some conservative, pedantic pre-Tezuka shōjo manga about how little Chieko became a good obedient wife and waits every day to serve dinner to her salaryman husband because he gets so tired from perpetuating the Japanese economic miracle.' - Carlos Santos, Anime News Network"

Boku no Hatsukoi o Kimi ni Sasagu received the Shogakukan Manga Award for shōjo manga in 2008. The seventh volume of Boku no Hatsukoi o Kimi ni Sasagu was ranked 5th on the Tohan charts between April 25 and May 1, 2007. The eighth volume was ranked 5th on the Tohan charts between 24 to 30 July 2007. The ninth volume was ranked 3rd on the Tohan charts between October 30 and November 5, 2007. The tenth volume was ranked 5th on the Tohan charts between 22 to 28 January 2008 and 1st between January 29 and February 4, 2008. The eleventh volume was ranked 5th on the Tohan charts between 22 to 28 April 2008 and 4th between April 29 and March 5, 2008. The twelve volume was ranked 4th on the Tohan charts between August 26 and September 1, 2008.