Koei Tecmo is home to many iconic and beloved franchises. Many of them found homes on the PS4 like the Dynasty Warriors series but others like Ar No Surge have not. Thankfully this is changing a bit, thanks to the PlayStation Now subscription service. If you pay monthly, you can stream PlayStation 3 classics on your PS3, PS4 or PS Vita (even recently including PC support) and from personal experience, it works great most of the time.
Various games from the Koei-Tecmo library are now part of the service and the full list can be found below.

The following games also included Dynasty Warriors 6 Empires, Bladestorm: The Hundred Years War, Warriors: Legends of Troy, Quantum Theory, Ar Nosurge: Ode to an Unborn Star, Samurai Warriors 4, Yaiba Ninja Gaiden Z, and Ninja Gaiden 3 and more. The games announced will be playable today with an active PS Now membership.

Source: The PlayStation Brahs via PlayStation YouTube Channel