I am beginning to suspect I've found a new and unexpected interest in isekai light novels, but only the ones where the premise is completely stupid. The first one was this book about someone who entered another world in the form of a vending machine. This example, by contrast, has Touya, a hero who remains human but gains incredible power during the transition. That power? To summon a magical bathroom wherever he is, in the form of a Roadrunner style door that appears on the nearest wall.
As you can probably guess, this is a power which appears utterly useless at first glance, but turns out to be very handy indeed through a series of convenient plot points. What's that? Your land is in drought, and you need a lot of water from nowhere? Will that be hot, cold or sparkling? And we need to travel carrying an awful lot of supplies to make the journey there, but can't fit much in the available carriages? It's fine, put it in my magic bath.
Other advantages include the bath water (being made of magic) acting as an anti-spell defence, the soap being of such high quality when compared to the medieval standard that it's worth a lot of money, and that it comes with a built in hairdryer. That last one is more important than you might think, as constantly running a hairdryer (powered by his magic) results in his MP going up and him becoming an incredible wizard. (And having a blow-dry to die for.)
Which is how this manages to turn relatively quickly into a mostly by the numbers exploration and adventure series. He's naturally overpowered, but so are his various colleagues, as for once, more than one person has been summoned. There are five of them, but only him and Haruno, a young woman of whom he's rather fond, are popular with the nearest goddess. The other three are more agnostic, working together with the royal family. All five of them head off in their separate directions however, so this is mostly about Touya and the harem of women he builds around him by the magical power of having a bath.
Trust me, there is more ruminating on the ethics on who it's okay to get in a bath with in this than I ever possibly expected. Seriously, trying to get in the bath with someone is pretty much his main motivation. It is ridiculous. And it only gets worse when he realises that levelling up means his bath gets bigger, and more than one person can fit in it at a time. By the way, that levelling up? It's done by collecting other goddesses for his dream harem. (Dream as in when he's sleeping, not as in ideal.)
It's very silly and the plotting is rather simple, but I didn't have a terrible time reading it. There's about five volumes at this point, but I don't think I'll need to read quite that far through it. I've satisfied my curiosity, and can probably stop now.