Well what comes to my mind thematically close to this (hetero, sidescroller) are these (though none of them is better than Syahata, this game is fairly great):
Anthophobia by Terrarium (Lots of content and fairly good)
Ghost Hunter Vena by Vosmug (Quite good as well)
Parasite in City by Pixel Factory (Shorter but good)
Mystic Knight Maya by Mega BlueBall (One of my favorites, but its also a platformer so little bit different gameplay)
you might also like..
Night of Revenge by D-Lis (platformer fighter, kinda difficult but BEWARE: some parts are gory)
Captivity by Perveloper (that is without much story but basically surviving endless waves, but levels and animations are cool)
Zetria by Karnedraws (looks good but afaik there is only demo right now)