This is the SPECIAL Mode boss for the Pre-anniversary event of Priconne's 3rd Anniversary called "Connecting Bonds, Linking Hearts". It is a bit of a sad story but this boss is unrelated to it somehow that's why it looks so basic. This boss shouldn't be too difficult if you're a late game player already as usual. If you're somewhat in the middle, it might be challenging due to its damage and your lack of damage against its minions. You should prepare at least Yukari for the magic barrier in case you find it this boss' UB being too painful for you.
For Modes 2 and 3:
If you don't have New Year Kyaru, you can just use a physical team. It'll surely take 3 turns but it doesn't matter.
For example, you can use:
Akino 6*, Rei 6*, Yukari 6*, Aoi 5*, Suzuna 6*, Christina 5*, Princess Kokkoro 5*, Labyrista 5*, Hiyori 6*, etc.
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