pixiv_mahou_gakuen
Pixiv魔砲学園 (Pixiv Mahou Gakuen, Pixiv Magical Cannon School)
A pixiv project started by Nanaroku (fortress76). This tag includes Pixiv Mahou Gakuen 2.0.
It's themed on magical girls in two Magical Academy Cities.
"Magical Canon School / Mahou Gakuen" is originally a sequel game to "Magical Cannon Wars / Mahou Taisen", a shoot 'em up game for android. The game version of "Mahou Gakuen" is still not released yet.