This is a small little game mechanic that exists that wasn't touched on before; Companions! This was mentioned in one of the earlier chapters by Mama to Levania when she asks on if he would like a plush toy or something else.
These would act as a one-time use skill per fight, and each party member of your team could have one Companion (for a total of three different Companions). You could upgrade these for greater effect on their strength.
Part of the NieR Replicant crossover.
Part of the NieR: Automata crossover.
Part of the NieR: Automata crossover.
Part of the Drakengard 3 crossover.
Part of the Final Fantasy XIV crossover.
Part of the Dragon Quest X crossover.
Part of the Persona 5 crossover.
Above is a full list of Companions! Some were exclusive to events and crossovers, and as of such they are noted if they were from a crossover or not.