I don't know why you find it stretched, I got them from the game though
This is the original: cf.static.r.kamihimeproject.dmmgames.com/scenarios/bgimage/0074s_reizan_00-53c56248e1af4fe39c1f2d280d079b91718b249d.jpg
And this is the hd version: cf.static.r.kamihimeproject.dmmgames.com/scenarios/bgimage/0074s_reizan_00_pc_h-53c56248e1af4fe39c1f2d280d079b91718b249d.jpg