What a wonderful series! While it is a simple romcom with a gimmick, I think it works really well! Plus, the spirit is entertaining in its own right!
I like all of the characters (except the annoying rival towards the end). Torii is a fairly simple MC, but he has just enough going on that makes him not just a complete carbon copy of the "everyman" MC. Even better, Kirishima is a great female lead that puts in effort to win Torii's heart without being overbearing and really pushes when needed. I really liked the secondary characters, especially Himenomiya (I love her design so much!!)
Of course, there is the spirit that haunts Kirishima (called Reiko from here on) that plays a main role in the story. A lot of the time, I find the romcom gimmick to be frustrating, but Reiko pushes the plot forward when needed and expresses how the reader may feel during a moment (at least for me she generally did). When something funny or interesting happens, she laughs, and when someone interrupts a good moment, she flails in frustration. Her creepy art always brings a unique life to a scene... I found myself screenshotting them and sending them to friends as I read.
9/10 I highly recommend this romcom with a gimmick. I think it excels in that regard, making the tired slow burn innocent romance fun and fresh with Reiko to help do so. If you aren't into this genre and theme, then this manga will not change your feelings. I think I'll come back to this one on occasion for the laughs and the fun story and art.