THIS IS NOT AVAILABLE IN ENGLISH YET. DO NOT BUY IT EXPECTING AN ENGLISH TRANSLATION TO BE INCLUDED.
Tsukihime -A piece of blue glass moon- is available on both PS4 and Nintendo Switch. In order to purchase Tsukihime digitally, you will need a Japanese account on the platform of your choosing.
If you're looking to get a physical copy of Tsukihime, you can use Amazon, which is just a sign-up and buy type of deal, and will ship to you directly. Be wary of the listed shipping price.
Translation (In progress) available here from Tsukihimates. (I'll add a button here soon)
*"First Edition" comes with a big box whilst the "Normal version" is just a standard game case.