Something's up with Soul and Maka's resonance, and Soul is pretty sure he knows the cause, though he'll never admit it. A potential solution: hybrid resonance, transmitting their energy (and communication ability) through a third person. But when you might very possibly have feelings for your partner, and you don't want anyone to know, it's never safe to have anyone in the middle.

Planeptune is on its last limbs. Shares are at an all time low, Neptune has run herself ragged trying to support what's left of her country, and Nepgear has been comatose for weeks. Fearing the demise of their nation imminent, Histoire summons the other CPUs to request that they save Planeptune, using the only means left: One of the CPUs... must marry Neptune. [Part 3 is here!]