Bro legit forged the loli out of her, man, what the hell am I reading?
Trash.
You are reading Trash.
To expand on that very simple statement.
The MC will literally craft anything and everything. He will craft sorcery and magic greater than a great sage using a single swing of his hammer. He will craft saint level healing with a single swing of his hammer and we've already seen it. He will disarm his opponent with a single swing of his hammer to turn their equipment into raw material as he recrafts it mid combat. And he will craft body enhancement to himself with a single swing of his hammer.
And anything he fails to do is due to a lack of common sense, lack of self awareness and any excuse to get a lucky pervert situation or false tension and drama that will get resolved with a swing of his ultimate crafting ability.
But there is one thing he will never craft. A baby with his legendary sword, because he only knows how to swing his hammer and has no clue how to stab with his chunchumaru. So don't expect any birth rate increase involving his harem.
The story is trash. And you are better off accepting it as trash. Empty calories, ultra processed junk food manga. To be consumed and forgotten with no impact.