Doesn't help much, but the SHAFT logo on the layouts is not the one the studio uses now, and Wikipedia shows another logo used from 2010-17. So it's likely that your series is pre-2010, the period when the studio became really respected. You might browse through various "Ten best series from Shaft" websites and see if you spot either of your characters in a screen grab.
@sensei thank you so much for taking the time. Yes, it looks much like late 90s anime or something. I will def. try your tips to find more infos on it.
domo arigato ^_^
Also try the Facebook Groups for Anime Cel Collectors and RubberSlug & Anime-Beta. Some folks with photographic memory and wider experience than mine hang out there.