But he used healer's skills to take down the undead (even when swinging the sword). Plus he spent whole two years healing adventurers in the first town. If acting like a healer would level him up, he ought to be at least level 2 or 3, even if level ups were really difficult to achieve in that universe. Since nothing happened, one would think he needs to slay monsters for exp, like in the most traditional RPGs. Yet, nothing.