I'm so glad you love it! I indeed worked hard to be original and I'm glad it shows!
There are technically 9 datable chars, but one is not seen yet/revealed, and in addition to this there will be bonus content where you can temporarily play as a side character and date someone else (none of the above 9) but it's on rails.
There may possibly be a 10th (unrelated to bonus content) but depends on their reception.
The main chars can date each other, but things get more complex from there since only certain ones can date the tiger, croc, and bat. If you want a more precise list of compatibility at your spoiler risk, lmk and I'll share it with you!