When Manami declares her love for Danjuro, for a limited time, Danjuro is granted an increase in power. The more intense her love is, the stronger the transferred power will be. Since her love for Danjuro is extremely intense, the power-up granted to him is extremely strong. If the ability is activated in a moment of crisis then his power jumps exponentially. Therefore, when correctly applied, Lover Mode can be nearly unstoppable, especially if the person Manami declares her love for has a strong Quirk or is an extremely talented fighter.
Manami and Danjuro used this ability several times as a last resort to escape.