Sendoh seems like a friendly guy and well-liked by all. There seems to be no indication about him having close friends (although he seems to get along with everyone). I do see plenty of pictures of him with team mate, Hiroaki Koshino, thus the assumption that they are best friends. Aside from being incredibly talented, Sendoh is a natural leader and therefore earning him the title of the ace player and vice-captain of the Ryonan team.
Sendoh is one the most talented players around "Slam Dunk". He's a good shooter, nice rebounder and also a strategist of the game. He's able to play fancy offense but also capable of great defense stopping outstanding players like Maki and Rukawa. He's a very fast and flexible player. He truly is a Basketball Genius. Sakuragi likes to call himself the Genius, but Sendoh is called by others as "the true Genius".
During his first year of highschool he was a small forward and literally a scoring machine (similar to Rukawa), but on his second year he found out the virtues of passing the ball and assist the whole team. Sendoh is without a doubt the ace player of Ryonan. Along with Fukuda and Uozumi they form one of the strongest offensive team in Kanagawa.
Not only is Sendoh the ace player, he's also the support foundation of the team, when things are going wrong in the game, the Ryonan team members have faith in their star player. Sendoh is the sort of player who can bring up the best qualities of others.
Ryonan highly depends on Sendoh, when the team is behind, Sendoh will show his scoring ability again without losing the focus on the game. He knows what's the best course to take for his team. It's often said that Sendoh is the true captain of Ryonan instead of Uozumi, because he has the ability to calm down the team, and also fire up and unify the team. When Uozumi retires from the game Sendoh becomes the new captain.
Although Ryonan lost their game vs Shohoku and also their opportunity to play in the IH competition, Sendoh was chosen to one of five best players of Kanagawa. (The other four were Maki, Akagi, Jin and Rukawa.)
Sendoh usually lacks focus when he meets an opponent that's not very strong. (During that timeout in the Shohoku-Ryonan practice game, Sendoh wasn't heavily challenged thus while Taoka was prepping the team with a strategy, Sendoh was sitting far off munching lemons and not paying attention much to the ire of Taoka Sensei) His concentration is optimal when he's playing rivals such as Rukawa and Maki, such guys bring up the best in him.
Sendoh is also known to lose track of time. He was late at the practice match vs Shohoku, but his honesty ("Sorry coach, I overslept.") was so disarming that even Ryonan's Coach Taoka simply couldn't stay mad at him. He was also late on the training right after the district games.
Sendoh is known for his spiky hair and ever disarming smile. He stands out from most of the Slam Dunk characters due to his nice and warm personality. He always smiles and is also friendly as well as modest. He never loses his temper and shows respect for strong players although just as competetive as the rest.
He seems to be the only player in the whole SD who was not irked by Sakuragi's obnoxious ways.
Sendoh's biggest hobby is, besides of basketball of course, fishing. He also have a thing for lemons.