Guide to Get S+ Rank in Holy Night XIII
Don’t land ever on Kirin’s segment, get up to chain 4 asap, then try to get as many multi kills as possible as you advance.
On GV’s segment play same as with Kirin, try to kill enemies in quick succession with his arc chain whenever possible.
It’s actually a bit annoying because you’re lacking the aerial up slash on the demo which helps extend air time but it’s doable.
Main thing is Kirin’s section, stay aerial for the whole thing and get some multikills and you’ll rack up a lot of score. Then so long as you don’t get hit more than maybe once or twice at most for the whole level & boss you’ll get S+ or S++ depending on how good your score-building was. Boss’s attacks are simple but his super requires arc chain to dodge the final attack. The attack where he lands near the middle of the screen and throws scythes is a good opportunity to arc chain behind him (hold forward on arc chain to swap sides with the target, this is an important mechanic btw remember it) and repeatedly slash him risk-free.
It’s not a difficult game to understand and it doesn’t have any weird tricks or odd unexplained mechanics (unlike previous games generally did) so if you’re failing it probably is just not building enough score from staying aerial + multikills or getting hit too much.