Seconded. Great ero-horror game!
Here's a little extra information based on my playthrough: the protag and his little sister become stranded when an earthquake devastates their city. Eventually, they decide to leave the ruins of their home to find a better shelter or more survivors... something like that... only to discover tentacle infested zombies roaming the streets. Little sis almost becomes rape bait until they're rescued by another group of survivors taking refuge in a mall. Gradually, the group is picked off and turned into monsters, and the last handful try to make an escape.
There's a bunch of different endings - mostly bad - depending on who you managed to save along the way, a few different pairings for the protag, lots of tentacle and body horror stuff, and girls range from mostly young, moe types, to a couple more mature women.
The sample pics linked above hardly do the game justice, and even with a basic understanding of the language, the story really sets the tone way better than just looking at the images on their own.
