Are You Okay With a Slightly Older Girlfriend? Is great if you're fine with the premise of a 27 years old woman and a 15 years old boy dating, which wasn't a problem for me. The series technically is not concluded from what I heard, bit it reached a good stopping point.

Why Shouldn’t a Detestable Demon Lord Fall in Love?! Is ok if you are looking for something sickening sweet.

Guide to the Perfect Otaku Girlfriend: Roomies and Romance is an ok romance between otaky and gal, nothing particularly special but if you like the genre is a nice read.

Reincarnated as the Piggy Duke: This Time I'm Gonna Tell Her How I Feel! as others starsc isn't 100% romance but is more of your average fantasy isekai. I enjoyed it, although it's brought down a bit by the apparent inability of the author to stick to his ideas until the end.

Endo and Kobayashi Live! The Latest on Tsundere Villainess Lieselotte is a series I appreciate reading and I usually don't read villainess stories. It has a good romance and lots of nice characters. The version currently on sale is the manga, though.

My favourite is A Lily Blooms In Another World.
It's a fluffy lesbian romance with villainess tropes.

Lady Rose Just Wants To Be A Commoner! (Manga) I liked quite a bit. Though it's more comedy than romance for the most part. By the time it ends, the heroine has a love interest (having gotten rid of the rest of the reverse harem) but the relationship is really only starting.

A Lily Blooms in Another World - whoever myskaros quoted above absolutely nailed it. Serviceable ideas, which all get smothered by the breakneck pace.

The Emperor's Lady-in-Waiting is Wanted as a Bride - From the same author as I Refuse to Be your Enemy, and honestly, I'd say Enemy was the stronger series of the two. That said, Lady-in-Waiting isn't a bad series, by any means.

I Refuse To Be Your Enemy! As the other quote said, more Fire Emblem than anything. The series is about 2 parts war story to 1 part romance. Not ultra-grimdark or anything, but easily the most serious of the stories I've read from the sale.

A Royal Rebound: Forget my ex-fiancée, I'm being pampered by the prince! I don't know who myskaros was quoting there, but I'll be honest: I think they read the whole series and just forgot books 2 and 3. That series did rather drop off after the first book.

To give some context, Enemy and Lady Rose are series I bought from JNC. I think I bought Lily from Amazon years back, read it once, and promptly buried it in the metaphorical back of my kindle library. Lady-in-Waiting and Royal Rebound were both series I streamed but never got around to buying.

Credits: @Hylebos @unsynchedcheese @saffire

Culinary Chronicles of the Court Flower

I've read around five volumes of Culinary Chronicles, it's an interesting story set in a rear palace with some supernatural elements and probably everything you would ever want to know about pickling beds. I had to take a break from the series as it looked like it was setting up for some high drama in the future but I would like to return to and finish the series at some point.

Are You Okay With a Slightly Older Girlfriend?

Slightly Older Girlfriend is the same author as You Like Me, Not My Daughter?! and roughly the same territory as well. I read the first volume and a bit of the second volume, I recall a falling out over a comment on bloomers which, while educational, seemed a tad silly to me at the time and I never got around to reading the rest.

Slightly Older Girlfriend is sugar, and it's fine for turning your brain off and enjoying the ride, but I admit a bit of frustration in how the female lead is too hapless at times. Like "is she actually supposed to be a working adult".

The Reincarnated Princess Spends Another Day Skipping Story Routes

The Reincarnated Princess Spends Another Day Skipping Story Routes is a fun one, the protagonist works really hard in the pre story portion of the otome game setting she's reincarnated to in order to achieve a happy ending. Part of the uniqueness of the setting is that the love interests will all end up becoming horribly messed up people if Rosemary isn't successful in her various plans, like one of them will become a necrophiliac, one of them becomes obsessed with their deceased mother, that sort of thing. Adds a nice bit of tension.

Another vote for Skipping Story Routes. The main story is complete with a good ending though I see it continued with an after story I haven't read. In one startingly original scene there is a romantic misunderstanding but then gasp people actually talk to each other. That's a new one 😉

Reincarnated Princess Skipping Routes: "Reincarnated into an otome game" but the love interests are all supposed to be absolute monsters, so she spends her childhood running around trying to subvert their origin stories so she can romance the guard captain instead who is definitely not 15 years older than she is and then inadvertently invents socialized health care.

Lady Rose Just Wants to Be a Commoner! (Manga)

I read all of the manga for Lady Rose Just Wants to Be a Commoner! while it was prepubbing but I'd be hard pressed to summarize the plot at gun point, though there were a lot of dramatic twists and turns, it might be more exciting to read in one shot instead of fortnightly prepubs, I definitely feel like I lost the plot at some point.

Lady Rose: An interesting take on the "reincarnated into an otome game" where the story begins after the game is over and the protagonist has been expelled from society...as she intended, not wanting to have been a noble. But her past comes back to haunt her, in more ways than one.

Lady Rose is one of those stories which feels like it's from a transitional era. It's an otome game isekai, and assumes the reader is familiar with that sort of story so it can subvert expectations. However, the Big Twist of the story is the sort of thing which is familiarly mentioned offhand in early chapters of other otome game isekais.

Why Shouldn’t a Detestable Demon Lord Fall in Love?!

I might have read a volume of Why Shouldn’t a Detestable Demon Lord Fall in Love?! but I don't remember it too well, aside from the fact that it was probably fluffy and wholesome.

Detestable Demon Lord is indeed fluffy and wholesome, though it dishes out so much sugar and is perhaps too lightweight unless you're really in the mood for that.

Marriage, Divorce, and Beyond: The White Mage and Black Knight's Romance Reignited

I read the first volume of Marriage, Divorce, and Beyond: The White Mage and Black Knight's Romance Reignited, it had an interesting start and setting but I remember it being what felt like slightly torture porn for the female lead, it's probably one of those series better read in one shot rather than as prepubs, the setting was interesting, at least.

Reincarnated as the Piggy Duke: This Time I'm Gonna Tell Her How I Feel!

Reincarnated as the Piggy Duke: This Time I'm Gonna Tell Her How I Feel! was one of the first series I read when I started prepubbing on J-Novel Club. It's not particularly romantic from what I recall, much more shonen, so if you're looking for a break from the other romance stuff on sale then this might be an option? It's a rare example of a reincarnated into an anime setting series, usually reincarnating into a game story setting is strictly dominant amongst authors. It's been a long while since I read it though and I haven't read all the volumes so it's tough to characterize it. It wasn't the strongest of series and I wish they did do more with the female lead, but it was serviceable enough.

Piggy Duke: A fun take on "reincarnated into stories" where the protag tries to be a "shadow hero" no one understands but ends up on center stage every time. Was axed so while it has an ending it's not a very satisfying one. I think it has a lot in common with Finding Avalon.

A Royal Rebound: Forget My Ex-Fiancé, I'm Being Pampered by the Prince!

A Royal Rebound: Forget My Ex-Fiancé, I'm Being Pampered by the Prince! is a classic and somewhat basic romance story, I only recall reading the first volume but it seems popular. I found the one prince's special ability to be fairly bullshit in its convenience, though if you enjoy people walking into obvious traps then it will endlessly deliver.

I Refuse to Be Your Enemy!

I Refuse To Be Your Enemy: Also "reincarnated into an otome game", but the otome game is Fire Emblem-ish instead of the usual fare. The title that got me into reading these types of stories

A Lily Blooms in Another World

A Lily Blooms In Another World is "we have I'm In Love With The Villainess at home". It's serviceable for its premise, but there's a fair number of sudden plot crises which appear just to be as swiftly dispatched, like the author is struggling to go through a checklist of plot points within a word limit.