This is an old art of mine, way before I bought a proper Tablet to draw. This was done in Macromedia Flash (I guess it was MX) and with a mouse after scanning the original picture.
I always liked to work on Flash because unlike other vetorial apps, it was way easier to create, select and erase the curves. You got have a lot of patience to use Beizer curves to draw/trace something (and I don't have such patience :P)
Those characters are from the idle-rpg doujin game Sakura Clicker by Winged Cloud and I always liked Wanaca's artsyle and design. And I decided to make some of those girls wrestling each other.