Salary Lupin (주급루팡)

The protagonist, who was enjoying the RPG game Dragon Slayer Academy, succeeds in raising 1,000 S-class heroes as the strongest supporter in the game. One day, a mysterious quest window appears in front of him, and he is presented with a hidden quest that allows him to raise EX-class heroes that surpass S-class heroes. Upon accepting the quest, he finds himself transported into the game world of Dragon Slayer Academy...