"Angel Densetsu" centers around Kitano Seiichirou, a high school student whose intimidating appearance belies his kind and gentle nature. Despite his pure heart and altruistic behavior, Kitano's frightening looks often lead to misunderstandings, causing others to perceive him as a dangerous delinquent. This misconception follows him to his new school, where students and faculty alike assume he is a violent troublemaker.

Kitano's reputation grows when he inadvertently thwarts a group of bullies, further solidifying his image as a fearsome figure. His actions attract the attention of the school's delinquents, who either seek to challenge him or pledge their loyalty, believing him to be a powerful leader. Meanwhile, Kitano remains oblivious to the chaos surrounding him, focusing instead on his studies and helping others whenever possible.

The narrative explores the contrast between Kitano's inner goodness and the external perceptions of him, often resulting in comedic and heartwarming situations. His interactions with classmates, particularly Takehisa, a fellow student who initially fears him but later becomes a close friend, highlight the theme of misunderstanding and the importance of looking beyond appearances. The story also delves into the dynamics of school life, with Kitano inadvertently influencing the behavior of those around him, often leading to positive changes in the school environment.

As the series progresses, Kitano's reputation continues to grow, drawing the attention of rival schools and even local gangs. Despite the escalating conflicts, Kitano's unwavering kindness and unintentional heroism consistently turn potential adversaries into allies. The series balances humor and drama, using Kitano's unique situation to explore themes of identity, perception, and the impact of one's actions on others. Through its engaging narrative and memorable characters, "Angel Densetsu" presents a compelling story that resonates with audiences through its blend of comedy, action, and heartfelt moments.