This hack for Castlevania: Portrait of Ruin replaces Richter & Maria with Kris & Susie and Old Axe Armor with Lancer, all three being from Deltarune by Toby Fox. The additional modes where you play as these characters have been unlocked from the start, so no completed savefile is required.
Database match: Castlevania - Portrait of Ruin (USA)
Database: No-Intro: DS (all) (v. 20210227-111036)
File/ROM SHA-1: 382602E3615B2282EEAD584014125E71B5B0F033
File/ROM CRC32: 96DF4C4D