I feel like development is going kinda slow with Kurumi... Ikari and Kurumi are definitely my favorite though
Also how to update the game without deleting older one? I don't want to lose progress.
There are reasons Kurumi's development is slower than others, which will start to be addressed soon (she has 2 events planned for 0.9, hint hint).
In regards to updating the game, depending on your platform:
Windows/Linux/Mac: Saves are stored outside the game folder, so deleting the game folder should still keep your saves. It's also possible to just overwrite files in the old folder with the updated ones.
Android: Installing the new apk (whilst still having the old version installed) should overwrite the old app and keep your saves.