Ema Toyama is definitely a hit-or-miss creator. On the one hand, that does speak well of the breadth of her work, because her uneven track record is less a matter of not being a good author and more a product of the fact that she rarely sticks with the same subgenre (or demographic) twice. That means that if you loved Aoba-kun's Confessions or I Am Here!, Missions of Love and Vampire Dormitory may not have worked for you, while all of those may have left you cold if you enjoyed Kami Kami Kaeshi or Manga Dogs, both of which are totally different from everything else she's had translated into English. I Guess I Became the Mother of the Great Demon King's 10 Children (full title I Guess I Became the Mother of the Demon King's 10 Children in Another World) is her first foray into isekai as well as being a shounen series, and while she adapts to the tropes of both fairly well, enjoyment of (any of) her previous works may not make this a definite winner for Toyama's readers.

The story is, as is the case with over-long titles, pretty much what it says on the tin. When Akari was fifteen, her mother died protecting her from the inevitable runaway truck, although why she thought standing in front of said truck with her arms out would work better than, say, jumping out of the way is never addressed. Now a year later, Akari is basically going through the motions of life while still having a lot of emotional trouble dealing with her loss. She's reached the point where she's desperate enough to have a child herself in order to have a family again, and that's when a magic circle drops the floor out from under her. When she comes to, she's surrounded by demons and is informed that she is the Priestess from another world whose wish coincided with the Great Demon King's at just the right minute, so now she needs to pop out ten babies for the good of demonkind, preferably starting right this minute.

By this point the manga likely has either intrigued you, make you snort-laugh with its premise, or turned you off completely. It's worth mentioning that the entire book manages to elicit all three of those feelings depending on the chapter and scene. There is something decidedly uncomfortable about the basic idea of the plot, and almost nothing else in the book can detract or distract from that. Even though baby one, a daughter named An, is conceived by drinking a magic potion (and then birthed via a large egg), there's a pretty strong implication that demons also conceive babies the regular way; initially one of the king's aides tells Akari to spread her legs so they can get with the conceiving and later the king himself lays her out on the bed. It's only when Akari objects strenuously (to the filthy surroundings) that they go with the potion, so there's a good chance that things will end up there by the last few kids. The other major stumbling block for some readers is the fact that the manga paints breastfeeding as something sexual: while feeding An, Akari feels sexual pleasure. Since that's not how breastfeeding works (something Toyama likely knows, since she mentions that she had a baby while working on the manga), this is an issue, both in terms of remembering that breastfeeding is what breasts are for and in the sexualization of the female body.

If that falls flat as an attempt at humor, Akari's difficulties getting sleep with an infant are pretty funny, and the weird contortions she has to bend into in order to find just the right position to quiet a fussy baby are pretty good, too. There's also a decent story underneath the whole isekai babymaking aspect. Both Akari and the king are emotionally vulnerable, he because he's been raised without love and now sees how Akari mothers An affectionately as something he wants, and she because she is, as she is well aware, trying to recreate the warm family she lost with her mother's death. She's also concerned about the demons' quality of life overall, insisting on treating their wounds, teaching them to cook food that isn't roasted potatoes, and genuinely worried about the toll the war is taking on them. As a human, she's concerned about them, too, but with the way the humans of this other world enter the story at the end of the volume, it's starting to look like she ended up on the better side of the conflict.

I Guess I Became the Mother of the Great Demon King's 10 Children is a very mixed bag. It indulges in what appears to be Toyama's idea of “boy humor” (toilets, boobs, underwear) a bit too much, it makes some jokes that are in very poor taste (toddler An in a sexy outfit), but it also has an obvious heart underneath the shenanigans. It is definitely not going to work for everyone.