This character looks like a rather scary and horrifying version of the main protagonist’s sister. By the way, she died under circumstances that are not entirely clear. She is able to be encountered several times in Omori while you are playing. And she, while on the subject, is very out of the general style.
This is one of the tricks in this genre. Therefore, it is possible for players to be scared that something very non-standard appears. Then the effect is quite impressive. As you become accustomed to one environment and suddenly there is something different from everything else, it can be quite intimidating.
Furthermore, it has a chance to be found many more times. But to do this, you need to make the necessary choices. For example, if your sister knocks on the door, depending on what you decide, you will either be able to see her or not. In general, almost all events are built this way, and in general the plot is rather branched.
Moreover, it is possible for her to be found in various locations and appear quite unexpectedly. Therefore, be constantly on the lookout. Furthermore, the genre is horror, so you need to constantly be ready for something like that.
It’s also worth noting that since Omori has multiple endings, she shows up at different rates in different outcomes. Therefore, in some, she may be constantly somewhere nearby, while in others she may not be a frequent visitor to you. Moreover, it is important to mention that it also has many states. She may appear before you in a blue guise. This can be called her standard appearance. But besides this, under certain conditions, it is capable of being red. Therefore, try the game a few times to learn a lot more.
Overall, this character is pretty horrifying. Because after epic battles with other creatures that will meet on your way, you would not really want to see something of this kind. Therefore, try not to relax and then no one will take you by surprise. Then you are able to cope with any difficulties with ease and with the least loss.