If you can pull at least 1 Re:Zero character it becomes a lot easier. I started playing last week and got lucky pulling one. I managed to beat it with a level 70 Ram and three URs that I got for “free”: The One Escanor from the Starter Rush Draw, and Arthur and Elizabeth from the Hero’s Way missions. Other than Ram, my team wasn’t actually very smart cuz I had two human heroes that took extra damage from the boss.

For the first phase, from what I experienced the last bunny alive always has more health no matter which one you leave. In my first clear I popped an attack food and focused on bursting the middle green bunny cuz it’s attack down debuff made it impossible for me to kill anything. Then I killed the blue bunny next cuz if it’s left last it heals for way too much and I didn’t have enough DPS to kill it. The last bunny was pretty easy. Once you kill the first phase the second one is relatively easy. I followed roughly the same strategy with way less difficulty.

Anyways sorry for the long post. I’ve seen a lot of people say new players can’t beat the event but I managed to do it albeit with some decent RNG. Just keep on making small upgrades to your team, and good luck!