There is a download option on every page the game is officially posted by myself. This doesn't include gamcore, but itch.io, where you're at right now. On the game's main page on itch, you have a download button: https://ryensaotome.itch.io/renryuu
It's set to "Pay what you want", which means you can download it for free by picking $0.
You can also download the game from MEGA or Hi-Drive:
MEGA: https://mega.nz/#F!CpQXwBDS!wwZlWRrPWoGzZX5h0-MlRQ