Two solutions I can see, either level up the skill and it will unlock new abilities such as allowing him to transform from a female to a male and not just the one way change he already has. Second being that he has to eat something from a species that has a skill that turns a female into a male or check if the shop has a skill that Laura can buy with her goddess points, such as an inverse skill that reverses the abilities of a skill. The problem, and main thing that can make this interesting, for the first way is that there are two ways to level up the skill, either using it so you become more proficient or in MCs case eat more things with the ability. The prior problem in my opinion could go either way depending on whether the skill will level up through simply being transformed, defeating monsters while being transformed, or if it requires him to transform back and forth to level up. As for the second solution I can imagine whichever skill has a higher level would probably take priority. Also if he had transfered the skill that doesn't necessarily mean he will transform back either.