My younger brother became ridiculously strong when he trained as his sister told him

If you're an adventurer, it's normal to be able to do this much... Another world adventure fantasy of a younger brother raised by the world's strongest older sister! Shifa, a boy who longs to be an adventurer, is told by his respected older sister, Rose. Believing in the words, "If you want to be an adventurer, you have to be able to do this," he continues his training. Rose's special training, which provides thorough gifted education so that her doting younger brother does not end up in danger, She gradually escalates and becomes more and more harsh... After overcoming such intensive training in hell, Shifa stepped into the adventurer training school on a sunny day. There she was waiting - “Your ability is a bit abnormal!?” Apparently my beloved older sister wasn't normal