For you, the end-user, downloading a free fan game is a legal grey area known as abandonware/fan tribute . You are unlikely to face legal action because you are not distributing it.
Now, rally your squad, manage your chakra, and rewrite the history of the Shinobi War. Good luck, Kage. How To Download Nindo Shinobi War
However, because this is an unofficial fan game, you won't find it on the Google Play Store or Apple App Store. This leads to the most common question in the community: For you, the end-user, downloading a free fan
Not legal, but practical. Your risk is not lawsuits; it is malware . Only 20% of the search results for this game lead to safe files. If you download from a random blogspot blog, you risk adware or spyware. Good luck, Kage
Bandai Namco (the license holder for Naruto games) has the right to issue a DMCA takedown to the developer at any time. This is why the game is not on app stores. If that happens, the download links vanish.