It’s MS Paint with Layers.
The layout and features is very similar to Photoshop so it was easy to navigate and use. It has many similar if not identical [Photoshop] tools necessary to do simple image editing. Certain features are odd like the crop (select area then ctrl+shift+X) and esp. the selection move tool (works like Illustrator + Paint combined).
No pen pressure recognition. Not for creating painterly looking drawings.
Tags: Ao no Exorcist