Once again Eda-sensei blows me away. First it was with Bonnouji, I'd never read such a realistic love story before and it's been in my top favourite manga since I finished it. I found this one through recommendations and only then realised it was hers. Suffice to say she did a splendid job here as well. I started reading romcoms and romances for exactly the same reason as this manga's main theme. I'm still trying to work out what love is though I'm more satisfied with just being an observer. I don't have the mental capacity to start a relationship so I rather watch and mull itover by myself. Koi wa Hikari definitely gave me a big bite to chew XD and also taught me a lot, especially the afterword. I found myself straying off the main theme and just wanting the Kitashira route to be the ending when the manga isn't about that at all. I definitely have a different outlook on love now and will try to think about it in more unique ways like this.

The story is a straight 10/10, I'd give it an 11 if I could. It's not a romance, it's more like a philosophical paper trying to explain love. And I loved it. Every relationship is deep and nuanced and the characters slowly realise a somewhat concrete theory by the end. Just like Bonnouji it doesn't have any explosive emotions or doki doki inducing scenes but explores its themes seriously and maturely.
Again, 10/10

The characters are a 10 as well. Everyone goes through a major arc but doesn't completely change, more like they improve who they are. I percieved their growth similarly to what I went through in the last year going to therapy. You don't completely change character, you just realise some big things and get a new outlook on the problem that's been bugging you. And it doesn't have to be solved by the end, it's already good if you're placed on a more defined path, just like Saijou and Shinonome.

The art is one of my personal favourites. It compliments the story by not being flashy and makes at least myself relate much more because the characters don't come out cartoony. I also like the smug faces, did in Bonnouji as well.
I usually have a hard time ranking art as I'm not an artist but from an immersion POV I have to give it at least a 9/10 (10/10 is reserved only for Kotoyama-sensei)

So, I guess this one's a straight shot for me. It's masterfully written, very complex and explores themes I've never thought about before. I recommend it very much if you're up for some deep philosophy and keep away if you want romance (at least save it under 'plan to read' for when you want to think a bit).