Yes, someone who actually wants romance without harem in action novels, crazy I know. I don't really care about the type of novel : it can be cultivation, korean, RRL or even Kindle. JP LN are ok too but only actually good ones (like Rakuin no Monshou for example), I've grown a bit tired of your run of the mill mediocre LN tbh. No BL either btw. For cultivation novels I've already read most of the books by IET, TJSS, Mao Ni and even the few by HSP that arent harem so I'm running out of ideas here...
novels from cutefish that loves diving before Lord of Mysteries The First Order The Legendary Mechanic Monarch of Evernight I Shall Seal the Heavens?
I would recommend “The Rebirth of the Malicious Empress of Military Lineage” it has really clever scheming and quite comedic moments sprinkled here and there. It’s by far the best CN romance that I have ever read. The romance is a great slow burn (btw when I say it’s slow burn I mean it, the romance only begins properly heating up around ch 140) with really entertaining bickering between the ML and FML. They both treat each other as equals with respect and the translation by Zazajunnie is great. You can read the reviews here on NU and see for yourself how much people love it! ^_^
https://forum.novelupdates.com/blogs/novel-recomendations-for-royal-road.3877/ https://www.novelupdates.com/viewlist/20556/
I have another recommendations that i recently discovered, it is called «Ending Maker», it is Korean and has both action and a great romance between two lovable and engaging characters. The side couples and overall plot is also great!
Doppio Senso - Korean modern action and romance. The girl is a spy sent to infiltrate the guy's company. The guy is involved in the underworld and is a badass. The girl is tough. You also get the two of them POVs. Just read the first chapter and tell me if it doesn't read like a Hollywood action film. It is so good. The sex is also well written. It still has the best sex have read on this site.
For cultivation, maybe https://www.novelupdates.com/series/my-evil-imperial-wife-is-too-arrogant/ It's definitely romance with no harem. I actually like the romance in here. It isn't the focus as the ml doesn't even appear for most of the 197 chapters that's been translated, but they think of each other and are devoted and it's not an angsty separation either, it's just natural because they need to do their own things independently. No silly misunderstandings, and they're practically a power couple. Flaws might be that it's got some cliches like black-belly, face-slapping, got those arrogant young masters/young misses, but i don't think the novel over does it. The female lead is transmigrated with her past life's memories as a very strong cultivator. Her cheat is basically her knowledge. It's weak-to-strong, but her knowledge makes her very talented in practically everything and she is very talented herself, but it's not one where she can defeat anyone, she's just super talented for people of her generation. 197 chapters are currently translated and ongoing, mtl is complete. Maybe, just a suggestion.