That axe does not look like a farming tool. It looks a bit like a misshapen battle axe.
Spinning tops are kind of old. As in, the oldest toys known to man. Don't think they even have a specific origin either, just appears in many places. This is one of the oldest inventions an isekai protagonist has "invented".
Bad smell goes in, bad smell goes out.
If the effectiveness doesn't decrease if you dilute it, all you need is a single drop, and you can dilute it endlessly. But I don't think that's the case.
So if you use a little extra magic growing plants, you could end up with a cute pet? Neat!
To be "so familiar with the shape" when it comes to swords, you have to have years of experience forging them. It's a very exact science, and takes more time getting the right shape even for experienced smiths. It's also got a rather small edge compared to katanas. One benefit of single-bladed swords is that the edge can be the entire width of the blade, while double-edged can be at most half. Not mentioning the handle and length.
He also wouldn't end up in that pose after that cut.
Can't he just re-shape the blade since it's made out of slime?
just some head up when people going to complain about katana latter,
There are things wrong with it even taking what you said into consideration.