UR Tears to Tiara Kakan no Daichi ティアーズ・トゥ・ティアラ Portable 04 Focused Grind to Converted Previous Rank A Recorded Story Battles to Rank S with Proof

If you want to get Rank S on all PSP version story battles, it's best you only get at most 3 story characters to max exp level, plus Taleshin, since he won't be available in the last sets of story battles.