They are half-sisters.
The Marquis Tassan's wives are all official. Six of them.
Two humans. Two beastfolk. One Fawn. One elf.
Edda and fairials are not among them.
Side note: beastfolk parentage is pretty much random.
A fox-folk mother having a rabbit-folk daughter happens all the time.
Eldest sister: Ekahi. White horns. 33, unmarried. A Fawn.
Heir apparent. Currently serving as acting lord. Earnest and strict.
Tends to be a bit pushy. Admires Axe's swordsmanship.
Struggles with her sisters. When she drinks, she... Has a Relic.
Second sister: Dova. Elf. 26, unmarried. Dark-skinned.
"Ah, yeah" is her catchphrase. Refers to herself in third person as Dova.
Looks like a female alternate-color Rel. Wants to get married. For some reason, she's in a rush about it.
Wears a monocle. Serves as deputy to the acting lord. Has a cosplay habit.
No combat ability. Has political power. No Relic.
Third sister: Tuli. Rabbit-folk. 25, unmarried. Personality is similar to Mineha.
Full of wasted motion. Equally clumsy.
Tsundere. Twins with the fourth sister. Has a Relic.
Fourth sister: Chaharu. Rabbit-folk. 25, unmarried. Highly aggressive.
She's convinced she's fallen behind despite having a lifespan of a thousand years.
In a sense, she's the most proper marquis's daughter of them all. She worries about her younger sisters more than anyone.
Twins with the third older sister. No Relic.
Fifth older sister: Fum. Fox-folk. Cursed with bad luck. When there's a two-choice pick, she always gets the wrong one.
Sometimes she's struck by Rube Goldberg–style misfortune too.
She's absurdly tough.
Despite having nothing to do with it, she was caught in the crossfire when an undead's rotting-meat pie was thrown at the thirteenth younger sister.
She loves romance novels full of blooming roses. Has a Relic.
Sixth older sister: Shesh. Black horns. Fawn. 22 years old.
Make eye contact with her and she attacks you. Is her personality similar to a monster's?
Harsh tone. Dual-wields a longsword and a saber.
Likes romance novels. Weak against undead and dark places.
No one is allowed into her fancy room crammed with stuffed animals.
Works as a mercenary bodyguard. Skilled at embroidery.
She's the one who makes the plush toys that the thirteenth and sixteenth younger sisters have.
Has a Relic.
Seventh older sister: Syuu. Black horns. Fawn. She calls herself "atasha."
Extremely long golden hair that coils around her body.
Drop-dead gorgeous. The kind of beauty that makes everyone turn their heads. She has zero awareness of it and zero interest.
Selfish as they come. A rule-breaker. She's already suffered the consequences more times than anyone can count.
She admires the witch who's a Rank I delver. Has aspirations of becoming a delver herself.
Her father, the Marquis personally, has issued a ban: "You are far too dangerous — absolutely not."
She occasionally runs away from home. Takes on gold-rank lower-class monsters one-on-one.
Wins despite sustaining near-fatal injuries. No Relic. In a sense, she's a monster herself.
8th sister: Samarnia. Elf. Brilliant. Smart. Skilled with a bow.
Strong writing skills. Black hair, silver-rimmed glasses.
Is she writing something? She likes Rel and Dova.
She likes them so much she's creating detailed profiles on both of them. Has a Relic.
9th sister: Ennea. Tanuki race. Chestnut hair and pale green eyes.
She's always sleeping. Has a Relic.
In truth, she's a Rank II delver — the "Sleeping Explosion King." Has a figure like a cow, complete with an enormous bust.
She has a safe. Nearly killed Juicy with those breasts.
Has a Relic. Refers to herself as "Poko."
10th sister: Ashara. Tanuki race. Gluttonous. Banned from food stalls.
Actually, she does have food she can't handle.
Once ate an entire cow, leaving not even the bones behind.
No matter how much she eats, she never gains weight. No Relic.
11th sister: Bearia. Universal human race. Leaves the kitchen in ruins after cooking.
Her cooking skills and taste are even more of a disaster.
Her dream is to become a chef. Has a Relic, but it has nothing to do with cooking.
12th sister: Elva. Elf. Has her sights set on marrying rich. Tears are a woman's weapon.
Radiates cuteness and charm at every opportunity.
Thinks her other sisters are out of their minds. Especially Zecatria.
No Relic.
13th sister: Zecatria. Universal human race. Tricky. The most dangerous one.
Fights a lot with the 6th sister.
Once threw a meat pie made from undead flesh at the 5th sister.
Has also fed undead meat pudding to the protagonist, Rel.
Loves undead. Wants to become a delver specifically for that reason, but she's physically weak.
Her personal room is a hereditary ancestral tomb. A shut-in.
Dreams of one day visiting the Tomb of Death. No Relic.
14th sister: Juicy. 13 years old. Werewolf race.
Aspires to be a delver. Quiet personality? Has the cutest looks among all the sisters.
In truth, she's the most combat-oriented of them all. A born grappler.
Being a dog, she has a master-servant dynamic, a servitude complex, and a desire to be kept as a pet. (She's not self-aware of this.)
Has a Relic.
15th sister: Kinse (Togo). Rabbit race. Loves trivia. Especially fond of useless knowledge.
Respects the 8th sister without knowing anything about what the others have been through.
Constantly thinks the other sisters' quirks are too over the top. No Relic.
16th sister: Sedichi. 8 years old. Fox race. Poetic. Refers to herself as "this one."
Silver hair and golden eyes. Loves cryptic remarks and poetry.
Impossible to tell what she's thinking.
She's cute as an angel, so I'll let it slide. Always going on about stars and swirls.
For some reason, she knows everyone's secrets, their pasts, and their futures. Has a Relic.
17th sister: Sorae. 0 years old. Wolf race. The fourth wife is currently pregnant. Six months along.
Only Rel doesn't know. Has a Relic.