Hummm I am not an expert on this cultivar but it seems suspicious .. having that current sunlight arraingement is a JM growers dream ...about 6-7 hours of morning sun is perfect for most cultivars. Some will take full sun and some get best coloration in full sun, but except for a few really delicut ones mostly dissectums that love dappled shade or complete shade thay all thrive in your current conditions.Daves garden says sun to patial shade to just partial shade. The leaves are large and not thick though so it's possible...but I suspect if you put it in full shade youll not get the brilliant green or good fall color. One thing could be if it's close to that wall and it's white or otherwise reflective that may cause the burning and excessive heat...and there's always the soil that could be causing it ...just sounds strange you have the optimim spot for a JM... David

I don't know which shirasawanum you have, species? I have a few, including Autumn Moon. It gets perhaps 3-4 hours direct morning sun, is in a container, fairly pampered, and always shows leaf burn. The color it is known for lasts into late spring/early summer, but to give more sun would be disastrous. I think the substance of the leaves makes them prone to burn, despite what some reports say--that even full sun is appropriate. I've come to accept the leaf damage, and love it for its changing colors through the season, now just coming into fall color.