I assume you mean LN...? If you liked HakoMari, then I highly recommend Gekkou. It's only 1 volume, but it's definitely one of my favorite romance novels. It doesn't play out like your usual romance stories, it's really unique and the chemistry between the characters is amazing. The interaction between the two characters and the lack of universal morals and laws in them, along with the author's ambiguous style of writing makes it one-of-a-kind and highly entertaining to read. Also seconding Hikaru ga Chikyuu, it's a great novel that will leave with with a bittersweet feeling after every volume. This novel explores human relationships really well, and I love how the author does the narration. It is all done in an abstract third person, limited to one character’s thoughts and perceptions at a time. The way the narration shifts from one character to another gives much better psychological insight than anything else could. You can also give Sayonara Piano Sonata a shot if you're into the music genre. There's also Tabi ni Deyou, Horobiyuku Sekai no Hate Made, which is another interesting one-shot novel that reminds me of Naricissu and a little of Kino no Tabi. You can check out an old thread I made ~a year ago if you want a couple more suggestions, link is in my signature.