Only I Know that This World Is a Game: Volume 2 by Usber

Souma Sagara, a loner college student who finds himself teleported into his favorite—albeit buggy—RPG, doubles down on his bizarre circumstances and decides to make use of all the glitches, bugs, and secrets he knows to hack his way to victory. After all, failure in the game can lead to a very real death for this hapless hero!

Joined by the disastrous damsel Miss Train, an NPC programmed to kill anyone spending too much time power leveling, Souma does what gamers do best: bend the rules to min-max every stat he can!