Diane vs. Gowther is a battle between Serpent's Sin of Envy, Diane of the Seven Deadly Sins and Goat's Sin of Lust, Gowther of the Seven Deadly Sins.
In the capital city of Liones, Diane and Elizabeth discuss about their love relationships before encountering Zeal who appeared to have no recollection of his memories or his identity. Realizing this was Gowther's work, Diane demanded explanation from him, which the Goat's Sin of Lust explained that love was the only way to make Guila happy, as in manipulating her memories replacing Zeal in her childhood with his own to prevent her Demon transformation like the rest of the New Generation did when Hendrickson used Blood Awaken. That unorthodox method of his had angered Diane and the Serpent's Sin of Envy tells Elizabeth to go find Meliodas and Merlin.
Unwilling to let Elizabeth escape, Gowther attempts to attack the princess but Diane got in the way, grabbing his arm and pushed him back before shielding Elizabeth with her earth wall from Gowther's light arrow. Now acknowledging that Diane is a great obstacle, Gowther summoned his Sacred Treasure, Herritt to perform Blackout that apparently knocked out everyone in the capital in a three mile wide radius for ten minutes, leaving the two Sins still standing. Diane then summoned series of earth pillars once more at Gowther who easily dodged them as she declared that one has the right to take away their precious memories as she already got hers back and will not let anyone take it away from her again.
Dodging the earth pillars, Gowther fired a series of light arrows at Diane only for the shrunken Giantess to dodge them all easily. The Goat's Sin of Lust commended of her strength after analyzing her Power Level to be 950 even in her shrunken form with Balor's Power Eye before brandishing his Herritt again. Diane then made a hand seal to summon Fillet and Loin to corner Gowther but the latter used Hijack to take control of the earth golems and had them attack their summoner.
The Serpent's Sin of Envy punched through her Invasion-controlled golems and launched herself straight to Gowther, intending to knock him back to his senses and wake up. As the two clashed a giant flash of light illuminated throughout the capital.
Following the flash of light Meliodas, Merlin and Elizabeth arrived on the scene of the battle and after seeing Diane collapsed in exhaustion and Gowther sulking they wondered what could've happened. Realizing it was Gowther, the Deadly Sins captain demanded an explanation from the Goat's Sin of Lust who, after realizing his actions, demanded to be sealed away in armor once again before it's too late.