A majority of the game's assets are reused from other games. The music and sound effects are gleaned from Bomberman Online Japan, while a sizeable chunk of the level graphics are plucked from Bomberman '94.
In the "assets/result/ssa/" folder are two sprites of Bomberman, found under "Draw_01.png" and "Failed.png" respectively. They're in a smaller scale than the usual graphics, and are inflated to 3x the size (they've been reduced to their original pixel size here). I can only imagine these are remnants of the original Bomberman graphics before they were uspcaled. (on that subject, does this game reuse the Bomberman graphics from another game, or are they brand new? I don't know myself!)