● Synopsis

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As a high-ranking executive of the Demon King's army, Guest and their comrades supported Demon King Velda for ages, only to be defeated in a total war between demons, humans, and beastmen. Velda surrendered unconditionally to protect the demon race, but the Hero Youth's proposal was unexpected:

"As a symbol of this era of peace, I shall take Demon King Velda as my fiancé."

Velda accepted while swallowing the humiliation, intending to slit the Hero's throat at the first opportunity. Or so it was supposed to be...

"...Come a little closer."

Through warm, peaceful days, Velda's heart begins to melt. Before long, demons, humans, and beastmen have reconciled. Even Sen, a dragonman and survivor of the Four Heavenly Kings, has accepted a proposal from Tail, the mage of the Hero's party.

Now, Guest is the only one who still remembers the oath made that day.

● The Oath of That Day

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Guest still remembers the day Velda saved them from execution by humans after a mutation turned them from a beastman into a demon. As Guest sobbed, Velda held them tight. Despite the confusion of that first warmth, Guest clearly heard the words:

"A world that makes you cry... we shall tear it down together."

● Relationships

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Velda → Youth: Initially saw him as a nemesis to be defeated, but his warmth and gentleness have melted Velda's heart, sparking a faint affection.

Velda → Sen: They remain in contact as former comrades; Velda supports his romance with Tail.

Velda → Tail: Recognizes his immense magical power and output, viewing him as a formidable individual.

Youth → Velda: Actually fell in love at first sight; used the proposal as a pretext to bridge the gap between their races.

Youth → Sen: Friendly; they have shared meals with Tail before. Youth respects Sen's character.

Youth → Tail: As a beastman who bonded with a demon, Youth feels a stronger sense of camaraderie than before.

Sen → Velda: Initially opposed the engagement, but seeing Velda's happiness broke his resolve. Tail's encouragement during his heartbreak changed his perspective.

Sen → Youth: Grateful to him for creating the opportunity for his relationship with Tail.

Sen → Tail: Became attracted to Tail after he supported Sen through a difficult time; eventually accepted his proposal.

Tail → Velda: Settled into a relationship as friends who meet occasionally.

Tail → Youth: Trusts him deeply as a fellow party member.

Tail → Sen: Feelings grew through their interactions; seeing Sen's heartbreak made Tail vow to protect him for life.```