The author posts on FC2 video under the name of Horuakuti, you can check there for previews of ?his? characters' functionality. Note that, although there are videos on the channel of Mina Majikina, Eko (Arcana Heart) and Akiha, I haven't been able to find a compatible release of any of these characters. I do have a somewhat compatible (no stuffed sprites) Akiha that I could upload if anyone's interested. Needs some alignment fixes but that won't take too much effort.
Not counting personal edits, there are 6 versions of mating press Kuromaru available right now. This isn't any sort of official change log, just based on my own observations and hazy recollection. No direct links because the people at the mugenryona uploader/board have historically been a bit weird about that. Shouldn't be too hard to find yourself.
V1: 4shared.com/zip/bmhRswp3ce/press_test.html First iteration of the mating press, comes with compatible Saki Tsuzura. [hcf+y] to initiate press grab.
V2: mugeryona1528 Leg overlay functionality added, impregnation cut-in fixed. The leg overlay is only used while transparency is toggled off (press Up during the press animation, it's a bit inconsistent when it will actually work so you might need to hammer it some, and it's disabled during the insertion and cumming animations. Tap down to re-enable transparency). Note that leg overlay requires unique sprites and animations to work correctly, and turning transparency off will cause glitching in victim animations if they don't have the correct animations. Comes with compatible Millia Rage. [y] to initiate press grab.
V3: mugeryona1607 Ground press pulling-in animation added, anti-air press grab added. Victims caught by [qcf,qcf+x/y] Tentacle Bind while airborne can be caught by anti-air press; several of Horuakuti's videos demonstrate this combo. Press KO activates alternate "stuffed" victim animations. Drawing-in, anti-air press and stuffed animations all cause glitching in victims without the correct animations. Giant Cock Smash [qcb,qcb+y, costs 1 Power] now stuns victims like stun/sleep gas. Comes with compatible Angelia Avallone. Patch at mugeryona1615, adds press KO zoom in. V3-compatible Arima Miyako at mugeryona1634. [x+y] or [down+a] to initiate ground press (hits downed characters if used while crouching), [qcb,qcb+a/b] to initiate high/low-angle anti-air press.
V4: mugeryona1685 pre-KO impregnation activates "stuffed" victim animations for future press attacks, causes glitching in victims without the correct animations. Comes with compatible Kira Daidouji and Heart Aino. [x+y] or [down+a] to initiate ground press (hits downed characters if used while crouching), [qcb,qcb+a/b] to initiate high/low-angle anti-air press.
V5: mugeryona1725 Blood spray on insertion added. Major alterations to Time Stop super; Time Stop duration greatly extended, victims can be captured by ground and air press during Time Stop, Time Stop can be activated during press animation by pressing start, (as with transparency toggle, you may need to mash,) press animation repeats from insertion after cum while Time Stop lasts, damage to victims is "held" during Time Stop and applied when Time Stop ends, blood and cum spray are frozen shortly after creation until Time Stop ends. Be warned that the press animation tends to glitch out when used immediately after Time Stop is activated, so you should wait a second or so before using a press grab. [down+a] no longer initiates ground press. [x+y] to initiate ground press, [qcb,qcb+a/b] to initiate high/low-angle anti-air press, [d,d+start] or [start] during press to initiate Time Stop (costs 3 Power).
V6: mugeryona1762 All mating press animations now call unique victim animations and will not work correctly with characters that have not been specially modified for mating press. Sexsomnia functionality added; using ground press grab on a victim sleeping from kuromaru's gas ([qcf,qcf+a/b] for stationary/floating sleep gas or [qcb,qcb+y, costs 1 Power] for Giant Cock Smash) calls different victim upper body animation and sound, and kuromaru can breathe gas during press animations except for insertion and cumshot by pressing A (again, might need to hammer). Victim wakes quickly, but gas stacks. If gas is stacked heavily enough that victim sleeps through the creampie, press animation repeats from insertion. Comes with compatible Eko (Vanguard Princess). [x+y] to initiate ground press, [qcb,qcb+a/b] to initiate high/low-angle anti-air press, [d,d+start] or [start] during press to initiate Time Stop (costs 3 Power).
As always, if anyone wants characters edited for missionary and/or mating press compatibility, or to learn how to do it themselves, shoot me a PM and I'll see what I can do. Note that I don't have the skill to make anything from scratch; I need sprites and an existing character to work with. Do feel free to speak up even if you don't have either, as I have a large amount of content pulled from the uploader and imageboard that I might be able to repurpose into usable sprites.