The story of the movie is somewhat based on the plot of the most recent game, "Sakura Wars 3," released back in March this year. While the game features Lieutenant Ohgami, the main character who takes off for Paris, narrates one side of the story, the movie unveils the secrets behind Hanagumi. Ohgami leaves for Paris, consequently leaving Hanagumi without a leader; thus a new character will be introduced here. To be replaced with Lieutenant Ohgami is the former leader of Hoshigumi, Rachette Artile - a rationalistic and distinct individual, who brings about serious problems to Hanagumi. The members are now in discord with Rachette. Meanwhile, Teikoku Kagekidan was being threatened by some irrelevant demons and a new type of anti-kouma mechas, (brought by an american company) appears and tries to replace the koubu-kai. Having made repeated mistakes due to the absence of Ohgami, Hanagumi is now faced with an unprecedented danger, while the abolishment of Teikoku Kagekidan Hanagumi is being schemed.
《浪漫杀手》终于要被改编成一系列动画电影了，并将登陆Netflix！白石渡的漫画《浪漫杀手》自2019年济音社旗下的《少年Jump++》第35期开始连载，并获得了第2届“Jump竖卷漫画奖”。
松井贵博（山口胜平 配音）第一次看到冢本裕司（古泽彻 配音）是在游泳比赛中，天真的松井立刻就被裕司帅气的身姿所吸引从而深深迷恋上了他。可是松井不知道的是，在裕司健康爽朗的外表下，藏着一颗由于被压迫和控制而变得扭曲乖僻的心灵。
