WARNING: The following contains spoilers for Episode 12 of The Strongest Sage With The Weakest Crest, "The Strongest Sage Goes on a Journey Again," now streaming on Crunchyroll.
In Episode 1 of The Strongest Sage With The Weakest, Gaius induced his reincarnation to obtain the four crests he desired. In the era of his original incarnation, the four crests were considered the most powerful in battle. 5,000 years later, Gaius is reborn with the four crests as a boy named Matthias “Matty” Hildesheimer, although in this timeline, the four crests is rejected as the weakest. As such, he was only able to enroll in the second-tier magic school known as the Second Academy in the kingdom of Eis.
Throughout the series, Matty reveals that he retained the memories of his past incarnation and uses his past life experiences in battles against demons. He also reveals through exposition the magical tools he invented in his past life that allow him to win fights against demons with little to no effort. During his stay at the Second Academy, Matty befriended his classmates Lurie and Alma, although he hasn't said anything about who he really is to them. Along the way, he was also reacquainted with his old friend Iris the darkness dragon -- the only one who knows his secret.
After stopping various demonic invasions throughout the series, Matty encountered a demonic presence he couldn't beat: the ancient demon Zardias who knew him as Gaius. Since that discovery, Matty set about locating the demon, which required the use of an ancient device he invented. Unfortunately for Matty, Zardias broke out of his magic prison the moment he determined his location and set course for the kingdom of Eis. With his resident kingdom in danger, Matty tasks Lurie and Alma with retrieving an ancient sword he invented in his former life while he battles Zardias alongside Iris.
The fight against Zardias proves to be nothing like Matty's earlier battles. Zardias is a lot stronger and deadlier than the demons Matty previously defeated, and his strategies don't work on the ancient demon. On top of that, Zardias shows he has tricks of his own, one of which ends up wounding Matty. This forces Matty to realize he'll have to sacrifice his current incarnation to defeat the demon, or humanity is done for. Since letting humanity die is not an option for Matty, he contemplates using his remaining magic to kill the demon and perform another reincarnation spell to save himself.
While reincarnation is Matty's only viable option in a deadly situation, there's one problem: if he reincarnates into another future timeline, Lurie and Alma will no longer be part of his life, as they will be long dead. Realizing he has grown fond of both girls and wants to remain with them along with Iris, Matty decides to hold off the demon a bit longer until Lurie arrives with the sword he needs. While Lurie does succeed at her task, Zardias delivers a fatal attack on Matty when he's not looking, successfully killing him.
Seeing Matty brutally killed before her eyes proves too much for Lurie to handle. This feeling is only made worse by the fact she had given Matty the sword just seconds before Zardias impaled him with his own weapon. Before Lurie has the chance to grieve Matty's death, however, the sword in his possession activates and restores him to life. The sword also restores his magic, making him stronger and more powerful than before. This gives Matty the power boost he needs to destroy Zardias, which he does quickly without any consequence to himself.
In the aftermath of the battle, everything in the kingdom of Eis returns to normal as if the threat of Zardias never happened. Even after his brief run-in with death, Matty doesn't seem fazed by the events that transpired. Lurie, however, is very shaken by the experience and admits her feelings for Matty by hugging him. While Matty doesn't use this opportunity to reciprocate her feelings, he does decide to do something nice for her to subtly let her know how much she means to him.
While out shopping with the reward money he earned for defeating Zardias, Matty buys a blue stone that he reshapes into a pendant for a necklace. When he asks Lurie to meet him in private one night, Lurie thinks the intimate nature of their meeting is going to lead to them kissing. However, Matty only gives her the necklace he made for her.
Although Lurie is grateful for Matty's gift, she doesn't take it as romantic confirmation of his feelings. Matty also doesn't use this opportunity to tell her the truth of who he really is or his past as Gaius as a way of progressing their relationship. This indicates that while Matty does love Lurie, he also doesn't trust her enough to tell her his secret. As such, The Strongest Sage With The Weakest Crest ends its first season on a rather anticlimactic note.
