I'll Live a Long Life to Dote on My Favorite Stepbrother!

Alba, who possesses memories of his past life, moves to the duke's household with his remarried mother. There, his new stepbrother turns out to be Orsis—the character he adored most in the otome game he played in his previous life. Though Alba rejoices at becoming family with his favorite character, he simultaneously recalls: In the game, it was because of his own excessive pampering by his stepfather that Orsis was plunged into tragedy.

Shaken by his encounter with Orsis, Alba suddenly collapses from a seizure. In this world, humans are born with magical power. However, Alba suffers from “Laonen's Dysmagia Syndrome,” which prevents him from controlling the release of his own magic. When he regains consciousness, he feels truly welcomed as family as his stepfather, Hals, and Orsis offer him warm words.

To prevent the relationship between Orsis and Hals from growing completely cold, Alba struggles to improve their bond. Through Alba's straightforward words and actions, Hals begins to reevaluate his relationship with Orsis...

Just as Hals and Orsis' relationship was improving and things seemed to be going smoothly, they meet Orsis' grandparents at his birthday party. Facing harsh treatment from grandparents who don't think highly of Alba, Alba has another seizure...!?

Having regained consciousness, Alba resolves to live on to witness his brother's future. Relying on memories from his past life, he prepares to teleport alone into the Agate Forest in search of the medicinal herb that could become the cure for Laonen's Dysmagia Syndrome. However, Orsis spots him.

Orsis offers to accompany Alba as he heads to the Agate Forest in search of medicinal herbs. But they lose their way and find themselves wandering the forest. Then, Hals appears, alerted by Orsis's magic—but...

After persuading Hals, Alba heads out with him to gather the herbs for the special antidote. However, the herbs can only be found halfway up a high cliff, and Alba hesitates. While trying to figure out a way down, Hals makes a surprising suggestion...

The group safely descends into the cave. They discover plants ahead. However, since they don't know how to use them yet, they decide to return home first and see what happens. Upon getting back home, an unexpected event occurs.

Orsis heads to Hals' room alone to discuss Alba's puzzling words and actions. Yet he cannot hide his shock at the astonishing possibility Hals reveals. A few days later, standing in his home garden, Alba witnesses a scene impossible in the game.

Alba enters a mysterious botanical garden that has appeared in his home's garden and discovers the same plant he found in the cave. It is revealed that this plant possesses the ability to store magical power. To investigate its properties, Hals invites his friend, Marquis Valt, and his son Bruno—a love interest in the dating sim—to the mansion.

Bruno is deeply perplexed by how close Alba and Orsis are. Meanwhile, a name has been decided for the plant Alba and the others discovered, and progress has been made in their research. As they are discussing this, Bruno notices something.

While sketching Orsis and Bruno, Alba unconsciously draws their adult forms based on memories from his past life. Upon seeing the drawing, the two mistakenly believe that Alba has accepted his own death! Renewing their commitment to their research, they vow to Alba that they will succeed. And so, time passes...