Certain characters are exclusive to specific DLC packs and cannot be unlocked through gameplay unless those packs are owned. Part of DLC Pack 3. Momoshiki Otsutsuki
Playing through the core Shippuden story is the standard way to unlock characters like Kaguya Otsutsuki (by completing "Kaguya, The Violent Goddess Part 2") and Certain characters are exclusive to specific DLC packs
If you prefer not to play Story Mode, characters unlock automatically as you earn total Ryo across all modes (Free Battle, Online, etc.). Certain characters are exclusive to specific DLC packs