Character png from [180525][みらーじゅそふと] 君とつながる恋フラグ

fau

Hi.
Are there any way to get character png with transparent background from [180525][みらーじゅそふと] 君とつながる恋フラグ?

I just downloaded CG from Games CG forum, but found all CG are bmp with black background.
I also tried to extract CG from the game by myself, but none of my tools (arc_conv_r53, ExtractData120, X-Ripper_1_5) worked.

Could anyone tell me how to get character images with transparent background from the game?
Any help will be appreciated.