The first year I carried the Suntech Kurenai rods I had both the H and the HM series. Once while fishing with a friend who caught a bass of about 12" on the H33 I decided I didn’t like the bend profile in the late stage of landing a nice fish, when the rod is tipped back and the bend is the most extreme. It looked like too much of the bend was concentrated in one section, which I thought would increase breakage over time. Following that I stopped carrying the H series.
I have never asked, but I have assumed the H is Hard, and the HM is Hard Medium. I have a Suntech Kaname 2H and had a Field Master Honryu 2H, which I assumed were Hard Hard, or extra hard, but they were such different rods from the Kurenai or from each other that there was no way to compare them to get a sense of whether they were extra hard (relative to what?). Neither of them had a tight bend profile like the H33 did.
Suntech has a 3H rod, which was designed for fishing the deep pools at the base of waterfalls with heavy split shot. That would suggest that it is a stiff rod, but I have never bought one so I don’t know for sure.