This game's keyboard support is lazy to say the least. The buttons of a virtual controller have been mapped to the keyboard. This is what it looks like.


The face buttons follow the Dreamcast/Microsoft order. So, if you go in the menu and map "jump" to "A", the X key on your keyboard will jump.

In the game's menu, you can configure what the buttons of the virtual controller do, but not what keys on your keyboard map to which buttons.
So for example, by changing what the "Y" button does, you can make your S key jump, attack, shield etc. But there's no way to map any function to the H key, for example. There's also no option for WASD movement, which is by far the biggest offender.

If you REALLY want to remap the keys, it's not completely joever. Nowadays, most (decent) keyboards ship with software that allows for key rebinding, making macros etc. This would allow for remapping the keys, but will be completely different from vendor to vendor, so your mileage may vary.
There's also always the option to use a controller. The game only supports Xinput, so If your controller isn't supported by the game (like my 8bitdo Neo Geo CD controller), you can simply remap its buttons to the keyboard keys used by the game. Here's a tutorial .