k so i've made experiment. Created new save removed sd card, loaded back the old saves on to it but game still had new save...
So either game saves itself into rom or it saves itself somewhere else as well, gonna check if saves are still there on previous card, worst case it means i've lost my saves along with rom i've deleted.
EDIT: Unfortunately it seems i keep getting new save file even when i use my old sd card, so i can only assume game saves itself inside rom file.
It stings but after searching forums it seems it was common knowledge.
At least i'm going to remember it next time. Good thing it was only card2 game where i''ve actually made some noticable progress.