Manga with a boy who goes to school, and struggles, but eventually becomes a dragon slayer

Question

It is medieval fantasy, like kings, dukes, and royals. The main character goes to a prestigious school because of his female childhood friend who is also there. As time go on, he struggles to keep up with her pace since she is gifted. At first, she tries to help, but eventually she leaves him and he sees her with another man. After that, he leaves her alone, and now everyone makes fun of him at school.

He goes into the forest to get stronger, but when he enters, he meets a monster and almost dies, but is saved by this old lady. She ends up training him in the forest where she lives, but even though he gets stronger, he is still the laughingstock for the people in his school. Every day after school, he goes into the forest to train. One day, as he is hunting in the forest for training, he stumbles upon people in danger and saves them with ease. One of them is a student in his school and she finds out that he is actually strong and he gains her interest.

He and his master, the old lady who uses a katana, kill a dragon and he become a dragon slayer, which gives him more power. His powers were sealed, which is why he was weak.

Answer 1

This is Ori of the Dragon Chain: "Heart" in the Mind, also identified here.

Solminati Academy is a prestigious school that harbors the dreams and hopes of ambitious students. Our story resolves a young man named Nozomu Bountis who entered the school for his lover's dream. As time went on, his powers deadlocked and could no longer advance, and his grades fell. Eventually, his lover was stolen by his at the time best friend. Heartbroken and lost on what to do next, he focused even harder on his training. Eventually, he meets an old woman, who triggers the catalyst to his growth. The future is uncertain, but gradually, his world changes.

The main character enters an academy to be with his childhood friend and lover. While at the academy, his growth deadlocks while she excels, leading to them drifting apart, culminating in a rumor spreading around the school that he cheated on her.

He has an ability that explicitly restricts his strength:

He continues training by himself, in secret, despite being unable to become stronger within the academy. This is largely aided by an older female samurai he runs across;

Chapter 8 consists of him fighting against a powerful dragon alongside his teacher. He briefly manages to overcome his ability restriction and slay it, and absorbs its powers. He doesn't actually fully remove his restriction, it's just that he obtains an incredible amount of power from the dragon that even his restrictive ability can't fully contain.