Blue Ash King

The Blue Ash King is the king of the Mist Kingdom and is renowned as a "hero." He participates in the unsuccessful assault on the Southern United Kingdoms and later serves as a general in the Holy Key Expedition.

Attack on the Southern Kingdoms
The Blue Ash King is first mentioned by a nobleman who hires some mercenaries to aid him in the upcoming war. His butler reveals that the Blue Ash King was the expedition's supreme commander, and had brought imperial knights and axe guards. The nobleman then gloats that he has even more troops than even the Blue Ash King.

Later, after Female Knight and her troops successfully rout the disgruntled mercenaries, they receive "reinforcements" in the form of snow. Blue Ash King and Royal Prince Marshal have a strategic meeting, where the Blue Ash King bitterly acknowledges that the cards were against them. Rather perturbed that they had assembled such a large force for naught, he is reminded by Marshal that they had little choice in the matter, although Blue Ash King misses Marshal's small utterance that the people who were supposed to betray the Southern Kingdoms failed to do so. Marshal then adds that they still gained something out of it, revealing that they had captured the craftsman whom the Crimson Scholar had asked to build the first musket.

Third Holy Key Expeditionary Force
Marshal mentions the Blue Ash King when he and the Chief Strategist overlooked the progress of the musketmen training. Ever since the unsuccessful attack, the Blue Ash King was burning with a desire for revenge for the previous humiliation, and Marshal believed it wouldn't take long before another war would break out.

Final Battle
When the expedition manages to break through Gateway City's walls, Blue Ash King looks on in surprise. After he discovers the truth behind the feat, he angrily confronts the Lily Knight Captain, seeing the suicide bombers as a waste of life. However, she insists on calling the sacrificed soldiers "martyrs," and recounts their nights together, suggesting that he is using her as much the Archbishop used the soldiers. When he rebuts her by saying that he'd never slept with a woman he didn't love, she laughs at him and says that he was being absurd, then redirects the conversation again by telling him that they both had to see out the expedition to its end.

Later, when the Blue Ash King went to Gateway City to direct his troops, he was betrayed and shot by a Lily Knight while he was alone. The other leaders were informed of his death, although the circumstances were unknown to them until the Chief Strategist realized that the Archbishop had ordered the Blue Ash King dead. After Older Sister Maid and Royal Prince Marshal form a ceasefire peace treaty, the Blue Ash King reveals himself to be just barely alive to an also gravely-wounded Lily Knight Captain. Before he dies, he confesses his love to her, which causes her to commit suicide to be with him.

Relationships
Royal Prince Marshal: The two of them are on friendly terms, openly discussing war tactics with each other. However, Marshal's trust in the Blue Ash King seems to diminish slightly after the latter sides with the Lily Knight Captain. Nevertheless, Marshal mourns for him when news of the Blue Ash King's death reaches him.

Lily Knight Captain: Although Blue Ash King recognizes Lily Knight Captain's "poisoned wine," he falls for her anyways and is shown to have slept with her at least once. He takes her side when she and Marshal come to a disagreement, and before the initial assault on Gateway City promises to offer his victory to her lips.

Trivia

 * The Blue Ash King does not exist at all in Hiro Touge's manga adaption.