So I've been without my console games for most of this year and have been exploring a lot of different computer games in the meantime. Two of those games have been Yume Nikki and .flow which play exactly the same way, but have distinctly different crazy dreamlike imagery. There's no way to really accurately describe them, it would be better for you to give it a try yourself. They're free to download which is super awesome!
On the left is the protagonist Madotsuki from Yume Nikki, and Sabitsuki from .flow is on the right. There's only one item in each game that can kill npc's and enemies, so I felt like drawing the girls with their distinct weapons. Also the crazy background imagery will make sense if you play the games.
If you decide to take the plunge you'll be greeted with a crazy open world environment where you acquire different abilities. It's about exploration and trying to interpret what you find to understand the story. There's an endless amount of theories for both games, and it's unclear as to what the real story is which is part of the fun. Try playing them and see what you think!
I suggest playing Yume Nikki first as it is the original and .flow is basically a fan game, while .flow is on the same level of depth and quality as Yume Nikki, it came afterwards. The games are in no way connected story-wise, so playing one or the other first doesn't matter. In the end it's up to you!
There's also wiki's for both games, but I HIGHLY suggest you start playing the games and exploring on your own before visiting them.