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 one of the most attractive boys in the class (the other being Hayato Kamitani), his female classmates have complimented him on his "healing vibes" and being gentle when handling his brother. He has a soft, feminine appearance, which makes him easily believable as a girl when wearing a wig.
Ryuuichi is a kind and easygoing person. He easily befriends the children and is loved by all of them. When Taka is crying, he is usually seen comforting the sobbing child and is regularly sought out by the children when upset. He is also somewhat absent-minded, appearing to be completely oblivious to his popularity, particularly to the fact that Inomata Maria and Ushimaru Yuki have feelings for him. He mentions that he has never been in love with anyone before because he sees Kotarou as his 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 firstborn son of the Kashima family and 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, his 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 pretences that Ryuuichi join the academy's babysitting club and help care for 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 alongside Kamitani and the rest. 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.
- The "Ryuu" in his name 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.
- His voice actor in the anime is Kōtarō Nishiyama, who shares the name of Ryuuichi's little brother.