Kirito is a cool loner at school who avoids social interactions with his classmates. However, his life takes an unexpected turn when his father announces that he's getting remarried to a woman with a daughter. When Kirito finally meets his new stepsister, he's shocked to discover that she's actually his ex-girlfriend, Emily.

As Kirito adjusts to life with his new family, he finds himself caught in a love triangle between Emily and the student council president, Izumi. While Izumi tries to win Kirito's heart, Emily attempts to rekindle their past relationship and seduce him.

As their school's cultural festival approaches, Kirito becomes embroiled in a series of misadventures involving his love interests and various hijinks. But things take a dramatic turn when Emily reveals a shocking secret about their past relationship, leaving Kirito reeling with confusion and betrayal.

With the first volume of the light novel coming to a close, Kirito must navigate his complicated feelings for Emily and Izumi while dealing with the fallout of their secrets. Will he be able to find true love amidst the chaos, or will his past mistakes come back to haunt him? The future is uncertain, and Kirito's heart is in turmoil as he faces the unknown.