The Daiwa Expert Seiryu 55 is an ideal rod for modest fish in small to middle sized to large streams. Daiwa does not use the 6:4, 7:3 categorization for the Expert Seiryu rods, but I would guess this rod is a bit closer to a 6:4 than a 7:3.
The rod has a cork grip. The grip is described as a two-handed grip although it is a bit short for where I usually put my hands for a two-handed grip. The grip makes the rod heavier than a seiryu rod of the same length, but the extra weight is all right at your hand. The rod feels "different" than a seiryu rod, but it doesn't feel heavy.
Daiwa recommends a wide range of tippets - from a fairly standard tenkara tippet of 5X all the way down to 10X. The rod would work nicely for the "zero" niche within keiryu fishing, which utilizes extremely light lines and shot, and very small hooks to add nothing (zero) to the natural drift of the bait. The 55 length is short for a Zero rod, but for the Zero approach on a smaller stream it would do nicely indeed.
The rod has a firm enough midsection that you could easily break 10X on the hook set if you aren't very careful, but the tip sections are soft enough to protect the light tippet if the fish are under 7-8". The midsection is firm enough that with 5X tippet, you should be able to land 15-16" fish.
I can certainly see why Daiwa would describe the Expert Seiryu rod as an "adult play" rod. It is very clearly a rod that will be fun to play with.