Ryuuichi Kashima is the protagonist of the Gakuen Babysitters series. He is dearly loved by his only younger brother, Kotarou and the kids in the daycare.
He is of average height with dark hair and large eyes. Considered to be an attractive person (the other being Hayato Kamitani), the girls have complimented him on his "healing vibes"  and being gentle when handling his brother. He has a feminine appearance which is easily mistaken as a girl with a wig.
Ryuuichi is a kind and easygoing person. He easily befriends the children and is loved by all of them. He is also somewhat absent-minded. When Taka is crying, he is usually seen comforting the sobbing child. He appears to be completely oblivious to the fact of his popularity, particularly Inomata Maria and Ushimaru Yuki, as he mentioned that he has never been in love with anyone before due to Kotarou as first priority.
Despite his gentle personality, he tends to speak his mind when he feels strongly about an issue. For instance, on seeing Hebihara coldly pushing his son, Hayato, away, he shoved angrily in Hebihara's hands his report which included details of both his sons' happenings in the daycare room as well as the recent photo with the other fathers of the children, noting Hebihara's negligence as a father.
Ryuuichi is the first born son to two unnamed parents and the older brother to Kotarou. As a child and even after Kotarou's birth, Ryuuichi considered their parents "free spirits" who loved to travel and explore new places, which often left Ryuuichi alone to take care of Kotarou. Shortly before the start of the series, he and Kotarou's parents tragically die in a plane crash while on holiday, leaving the two brothers as orphans. Coincidentally, the chairwoman of Morinomiya Academy's son and daughter in law also died in the same plane crash, and at the memorial the two brothers catch her eye because they were the only people other than herself who didn't shed a tear. This prompted the chairwoman to adopt Ryuuichi and Kotarou, but only under strict pretenses that Ryuuichi join the academy's babysitting club and participate with the care of the young children there everyday before school. He starts as a third-year middle school student at Morinomiya Academy and advances to its high school during the series. He is repeatedly noted as being very close with his brother, being considerate even on rare occasions when Kotarou has broken his things as a baby in the past. alongside Kamitani and the rest.
- The first part of his name "Ryuu" means "dragon".
- Ryuuichi is the type of person who would put "tongari" corn on their fingers due to influence from his father.
- When Ryuuichi first disguised himself as a girl, Usaida referred to him as "Ryuuko" to trick Kumatsuka Satoru. This caused Inui to fall in love with him (who thinks his name is "Inomata"). It has become a running gag for Ryuuichi to be put into a wig and disguised as a girl.
- His birthday is on the 30th of July, making his star sign Leo, but in the first edition of volume 11 the mangaka mistakenly describe him as a Cancer in the character profiles. She had initially decided to make him Cancer after having read somewhere that Cancer people are suitable for working in childcare.
- Ryuuichi is voiced by Yuki Kaji on the drama CD in May 2011.
- In the anime, he is voiced by Kōtarō Nishiyama, who shares the name of Ryuuichi's little brother.