Welcome to the fascinating world of Gensokyo, in which youkai (A term for all sorts of spiritual creatures), animals and some humans live, completely separated from our world by a magical barrier. The only gateway between the two worlds is the Hakurei shrine. Reimu Hakurei is the maiden working at said shrine. Whenever problems of supernatural causes (known as "Incidents") occur, Reimu goes out with her friends to investigate, eliminate the cause and hopefully restore Gensokyo to its equilibrium.

Kanan is a demon who descends upon the human world with one goal: to feast on the sweetest delicacy of all—young human souls. Disguised as a high schooler, she sets her sights on her first target, an unassuming boy named Youji Kyougi. But just as she prepares to claim her meal, things take a very unexpected turn. Instead of devouring him, Kanan ends up forming a "romantic contract" with Youji. For someone who's lived for millennia without experiencing love, navigating high school romance proves more terrifying than any hunt. Between awkward dates, hand-holding mishaps, and feelings she can't quite name, the once-proud demon finds herself flustered at every turn. A supernatural romcom about a lovestruck demon and the boy who was supposed to be her prey—sweet, chaotic, and full of firsts.

The entire universe is divided into the inner universe and the outer universe. The two universes are enemies of each other. The outer universe is ruled by demons, and the inner universe is divided into The Realm of gods, the Eternal Realm, and the Mortal Realm. In the universe, there are countless mortal worlds like the Tianfa Continent, and they are collectively referred to as the Jiutian Xin Region. In the field of Jiutian Xin, nine immortal emperors commanded all star fields in nine layers. Above the nine heavens is the realm of purification of immortal gods.

The Xuanling Sect, the head of the four major sects, came to Shuicheng to select disciples for the first time in many years. The Fang and Qin families started fighting openly and secretly around this opportunity that would determine their fate. In the end, Qin Nan relied on his dedicated training, excellent talent, and the God of War Soul obtained by chance, and under the fair judgment of the messenger Xiao Qingxue, he successfully reversed the decline and defeated the Fang family. After entering the sect, Qin Nan aroused the hatred of Ouyang Jun, the son of the sect leader, because of his involvement in Xiao Qingxue's forced marriage. In order to continue to become stronger and repay Xiao Qingxue's kindness, Qin Nan repeatedly defeated powerful enemies, won the first place in the Wanxiang Competition and the Outer Sect Competition, entered the Wuyuan Pavilion with the four major sect geniuses, and obtained the power to stir up the continent. A shocking secret, an appointment with Leng Feng to fight in the Palace of Life and Death, overcoming the siege of Linshui City by the Beihai family, exploring the Nine-Character Mantra Tower, and vowing to fight the evil forces of the sect to the end.