Kitazawa was Eiri Uesugi&#039;s tutor while Eiri lived in America with Tohma Seguchi. It was shown in the manga that Eiri and Kitazawa had a happy and friendly teacher and student relationship. The relationship often appeared more as friendship, despite that Eiri called Kitazawa &quot;sensei&quot;. Unbeknownst the Eiri, however, Kitazawa is a pedophile who has sexual designs on his young pupil.    Later on in both the manga and the anime, Kitazawa drops a bottle during the time he had Eiri trapped inside of the dark apartment one night. Two men enter the scene and he lets them, for a fee of $10, go &#039;first&#039;.    During the rape, Eiri gets a hold of a gun and shoot Kitazawa, killing him. Tohma Seguchi finds Eiri at the apartment and comforts him afterward. He feels responsible for what happened to Eiri because he was the one who hired Kitazawa as his tutor, and feels that he didn&#039;t look into him enough and could have prevented the disaster.    Kitazawa has a younger brother called Yoshiki, who is an MTF transsexual. In Gravitation 2, it is also revealed that he has a young son named Riku.  

Shindou Shuichi is a young, energetic, and optimistic rockstar wannabe. He’s in a band with his best friend and is determined to top the charts. When a romance novelist named Eiri Yuki criticizes his lyrics, Shuichi takes it badly and wants to make Yuki eat his words…but as he starts to follow Yuki around, Shuichi falls hard for him. Yuki, despite his cold and prickly demeanor, even seems to like Shuichi back! Still, Yuki has a past full of trauma that he’s never fully faced, and Shuichi discovers that succeeding in the music biz might cost him his soul. Can these two very different men support each other and make this relationship work? (Source: Seven Seas Entertainment) Note: Includes 2 extra chapters.

In order to heal the wounds in Eiri Yuki's heart, he and his vocalist lover, Shuichi, travel to New York to visit the grave of Yuki's first love and tormentor, Yuki Kitagawa. They discover that the first Yuki has left behind a young son, Riku, and so the odd couple take the boy back with them to Japan. When Shuuichi receives a kiss from nutty rival band leader, Ryuuichi, Yuki flies into a jealous rage, and he and Riku disappear, leaving Shuuichi to search for them in vain. 

(Source: Tokyopop)

All Shuichi ever dreamed about was following in the footsteps of his pop idol, Ryuichi Sakuma and the band Nittle Grasper. Together with his best friend Hiro, Shuichi's formed a band called Bad Luck and they've even managed to get signed to a major recording label! Unfortunately, the studio deadlines are looming and Shuichi still hasn't finished the lyrics for any of the songs. What he needs is a little inspiration... but he's been running a little low in that department lately. While Hiro recommends finding a girlfriend, fate has other things in store for him... 
Walking through the park late one night, Shuichi's latest lyrics flutter away and land at the feet of a stunning stranger that takes his breath away. Unfortunately, that mysterious stranger happens to be the famous novelist Eiri Yuki, who completely crushes the young singer by telling him he has "zero talent". Now, Shuichi's so annoyed that he's managed to finish his song just so he can find and confront Yuki once again. But, are his actions really motivated by anger, or has he actually fallen in love? 
(Source: RightStuf)

A series of very graphic adult Gravitation doujinshi by the original mangaka:
 
Panda パンダ (Yuki uke, Seguchi x Yuki x Tatsuha) (2006) 
Kumagorou くまごろう (Shuichi x Yuki) (2006) 
Capybara カピバラ (Eiri x Shuichi / Hiro x Suguru ) (2007) 
Sakana 魚 (2013) 
Hyoko ひよこ (2013) 
Ushi 牛 (2013) 
Chirimenjako ちりめんじゃこ (2014) 
Torokeru Pudding とろけるプリン (2015) 
Ookami 狼 (2016) 
Kitsune キツネ (2017)

Yuki Kitazawa