Can't go back to get Ballet shoes!!

[The Pest]

I'm fighting undyne the undying on genocide run, and I've completed pacifist and neutral, but I'm having a problem. Fighting Undyne is a pain in the ass on genocide run already, but without better items i think I'm screwed. So go back to try and retrieve the ballet shoes which i forgot about and some better health items, but the river man and the duck are gone! And there is no other path that I'm aware of that lets me go back.

If you've got any info ,all help is appreciated

[[RvB] RedArmyGrif]

Head to Gerson, load up on Crab Apples and grab the Notebook and Glasses.

[Nestle Crunch]

I would say keep the snowman pieces and the butts pie in the chest (better if you have them for a bad time) just do what RedArmy said, get the invincobility items.I also just beat geno undine, she is easy if you're not bad.