In detail, $f$ is corepresentably full on cores if, for each $X\in \text{Obj}\webleft (\mathcal{C}\webright )$ and each $2$-isomorphism
of $\mathcal{C}$, there exists a $2$-isomorphism of $\mathcal{C}$ such that we have an equality of pasting diagrams in $\mathcal{C}$, i.e. such that we have
\[ \beta =\alpha \mathbin {\star }\text{id}_{f}. \]