Gigantic Rider in 1RM

Reincarnated as a nameless commoner on Raniakea, the continent of magic and steel, with memories of 21st century Earth. To escape the life of a commoner, who is almost like a slave, he must lift the 'Magic Stone' and become a Giant Rider. ‘Straighten your back!’ ‘Tighten your belly!’ ‘Take a deep breath into the bottom of your abdomen!’. He uses knowledge from his previous life as a trainer to accumulate magical power as if he were exercising, and climbs the ladder of the social hierarchy....