How to open the Toshiba pr100 fan box

In other words, a notebook fan is usually cleaned up once a year and a half. When cleaning, the fan is usually removed, the fan box is opened, the fan blades inside are removed, and the blades, boxes, and shafts are cleaned separately. A necessary step is to open the fan box. In this case, it is to open the black fan box:

Originally I tried to clean up the fan of Toshiba's pr100, but this is a must-have link: The fan box seems to be unable to be opened. It looks like the complete shape of the removed fan, which is much smaller and thinner than the ThinkPad fan.

Look, compare it with your thumb to see how small it is.

From the aspect, we can see how thin it is. Look, I want to uncover the fan box, but the arrow points out cannot be lifted.

Let's look at the two big figures below: the small bumps pointed by the arrows cannot be uncovered.

Looking at the back, it seems like I am dying? Is there any way to solve this problem?

Problem:

How can I open the Toshiba r100 fan box? If it cannot be opened, can it be directly rinsed with water? Will the fan motor be broken if water is flushed?