My Bible is "The Otherworld Summoning Story"

Ernesto is the third son of the House of Violetti. As an adult unable to inherit the family estate, he chooses the path of an adventurer to make a living. All he can rely on is the barely functional unique skill "Magic Bullet" and the knowledge written in the family's secret tome "Otherworldly Summoning Tales." Despite being viewed with prejudice because of his brothers, who are "Disaster-class" level, he earnestly continues his trips to the guild each day. This is a modest tale of an adventurer's rise to prominence—a young man whose sword and magic skills are both second-rate, armed only with his beloved and biblically important family secret tome "Otherworldly Summoning Tales." The main story is complete for now.