Shuichi Takamizawa is a main character in the Midori Days anime. He is effectively a nerd who heavily enjoys hand puppets and a specific anime known as Ultragirl Marin. He is introduced very early in the series, and recurs throughout the series.
History (up to Schuichi's first meeting with Seiji)
Not much is ever revealed about Takamizawa. All that is known for sure is that he has gone to Seiji's class for quite some time. Shuichi tries not to draw attention to himself while at school, however he shows his true colors when he reaches the Blue Submarine doll shop.
Shuichi meets Seiji one day at the Blue Submarine, and engages him in conversation. Seiji becomes very unnerved that not only does a classmate know he has come here, but to add to it Shuichi appears to be obsessed with dolls; of which Seiji has a living one on his arm. Shuichi tries to see what is on his arm, but is unable to get a look, as Seiji knocks him out. At first Shuchi believes it's some kind of foreign hand puppet with very amazing gimmicks, but then comes to find out Midori is alive.
Shuichi is extremely obsessed with Ultragirl Marin and hand puppets to the point of being very creepy. He will obsess over these materials, and is content living his life as a socially awkward person. He tends to stray from conversation with the cast (outside of Seiji and Midori) mainly due to his rabid interests. His room shows a mass number of Ultragirl Marin posters, merchandise, and even figurines. He even falls for a girl whom looks just like Marin, and that is the only reason he falls for her.
Shuichi typically carries a hand puppet of Ultragirl Marin on his hand at all times. He uses ventriloquism to speak for the doll and give it a personality. His hand puppet is very reminiscent of the tsundere personality type, often chastising him for not paying enough attention while being overly excited at his confessions of love for her. He treats her as an individual, however (unlike Midori) she is only a hand puppet and no more.
Shuichi does fall for Midori at one point, but Midori manages to get him to back down from it quickly. His infatuation was mainly at the idea of a girl who would be willing to love him unconditionally and would live on his hand. Midori manages to make him realize she isn't a doll, and as such Shuichi realizes that Midori isn't the kind of girl he is interested in after all, and goes back to Marin. Despite this, he becomes good friends with Seiji and Midori.
In several instances, he is shown to be very sneaky and impulsive. His impulsive behaviors range from creative to disturbing. One example of disturbing is the request to see Midori in a bikini (which results in a headbutt from Seiji) while a creative can be his website and doll line. He creates an entire series of Midori hand puppet and sells them. This leads to very good profits, and he even shares the money with Seiji. He also at one point created a website upon which he took images of Midori covertly. These images didn't reveal Midori to the public, but rather were close up images of her that showed off her beauty while always being images from the waist up. When questioned by Seiji; Shuichi responded that the images were taken in secret due to the fact that photographs of her are much better when she is unaware of the photographer. The website was apparently critically acclaimed, and Midori even stated had been viewed over 500,000 times.
Shuichi is a good person at heart who is socially awkward. Seiji and Midori first figure Shuichi for being a potential future molester. This changes after a misunderstanding when Shuichi attempts to protect a girl he has a crush on from a gang member with his bare hands (the gang member being Seiji in disguise to which Shuichi doesn't know this). This reveals to Midori and Seiji that Shuichi is actually a normal person underneath his very unorthodox behavior, and is apparently more than willing to place himself in danger to protect others despite having no formal training in any physical manner; even when his opponent could very well be double his size.