Kasai Tatsuyoshi (葛西 辰由) is a character in the Higurashi no Naku Koro ni series. He is a member of the Sonozaki Group, and is employed by the Sonozaki family as a bodyguard to watch over Sonozaki Shion around the clock since she was sent to study at the private school Saint-Lucia Academy. He is usually always around when she needs him to help in difficult situations, and Mion mentions in the Sound Novel that Shion needs a protector, because people "do crazy things." It is also said that Kasai once had a leading role within the Sonozaki family until he retired due to an injury, then becoming the personal bodyguard and servant of Shion. If Shion wants to go somewhere, she is usually driven by Kasai. Although they sometimes exceed the distance limit set by her family, not to drive by Hinamizawa. He does very much for her, but when she confessed to him about entering the Saiguden at the Furude Shrine, Kasai told her that he would do his best, but that he can't protect her from the consequences.
Highly skilled with guns, he seems to specialize in use of a sniper rifle. In Matsuribayashi-hen, he displays extreme strength and combat experience while raiding the Irie Clinic, frequently subduing members of the Yamainu. He stated afterword that he vowed to never do some thing like that again. Kasai used to have a crush on Sonozaki Akane even if his boss is her husband. In Meakashi-hen Shion revealed that Kasai was badly injured once in a yakuza battle when he was younger and because of this he can only do safer jobs, such as protecting Shion.
Kasai is a muscular man with short brown hair and a beard, whose appearance is described as "intimidating." His age is not specified, although it is implied that he might be somewhere in his forties. He nearly always wears a black suit, and even when in disguise he wears his sunglasses.
- In the Steam version, Kasai's necktie has a skull pattern
- He is always shown to wear a small rhombus lapel pin on his suit. It's unknown whether this is only there for decoration, or represent something in the Sonozaki Group
- In Meakashi-hen, the final credits states that Kasai died in 2002 from liver cancer. However in Yoigoshi-hen, Kasai is shown to be alive and well, even though the story takes place in 2006.
- It's possible that in Yoigoshi-hen, his cancer is discovered and cured before becoming fatal
- Since liver cancer is not that common among healthy people, it's also possible that after everyone's deaths in Meakashi-hen, Kasai had developed some unhealthy habit (for example heavy drinking), which eventually led to him getting liver cancer.