Hakone grass is slow to establish and the clumps expand but other than that, a decently rich soil and adequate moisture should be all that it needs. It should be able to tolerate heat and humidity well as long as it receives adequate water. Hot and dry, not so much. In my climate it can take a LOT of sun. Here is 'Aureola' growing in almost full sun at a local botanical garden:

Maybe I had mine in too much shade. I think I will try again but add a bit more to my bed in the way of soil amendments. I did to a bit of reading and it does like rich soil (mine is basically clay).

My JFG/ Aureola is in full shade on north side of house & under Acuba ”Gold Strike” It’s slow to come out, especially this wet & chilly spring but it’s doing well with the shade & water from drips. It’s along a path edge & increasing in size each year. A neighbor across street has some in her east facing front yard with sun until @ 2pm - it’s also well watered & she’s been dividing hers each fall to keep it to size. We both have clay soil but well amended for planting. I am also in PNW zone 8 - south of @gardengal48 (PNW Z8/9) & we do have warmer summers & usually less rain than where I think she is - closer to Puget Sound area - I’m by Columbia River & Oregon border. BTW , I also have what I think of as a miniature version of forest grass -Japanese Sweet Flag Ogon. Not a true grass but looks like baby forest grass to me… I have it in hot west sun just off paver patio so a hot spot & it does great with drip irrigation.