VRMMO wo Kane no Chikara de Musou suru

The fabulously wealthy heir to the Tsuwabuki Concern, Ichirou Tsuwabuki, has arrived inside the next generation VRMMO, "Narrow Fantasy Online." His cousin Asuha has asked for his help in finding someone inside the game, and he's come to help her out. Of course, while he's happy enough to help his cousin out, Ichirou also cannot be satisfied with anything but total mastery of whatever he tries. He quickly proceeds to dominate the game world using his natural genius... and his wallet!

(Source: J-Novel Club)