This story got the best confession line ever in manga.

I must admit, the author got really good job putting everything to work out in this Hetakoi. I easily enjoy every page, and every second of this. It's easy for me to get the feel of falling in love, jealousy, excitement, happiness, and anxiety, or even anger while reading this. And after all that roller coaster of emotion, we got one heck of a confession line. I love it.

That in itself is good enough to make a good manga, but this manga is not limited to just that.
The characters are really well done. they got drawn really well. With point-to-point traits that is easily for readers to empathize. I especially like the male MC. He is caring, not only to those he like, but also to the one he doesn't like (He cares even to his love rival at some point). And it's just one of many likable trait he had. As the story progress, we get to see him maturing both in mind and in emotion.

The art is also excellent. Besides the characters, the world itself is a great work. Because this revolve around a hot spring lover club, of course there must be beautiful hot springs involved.

This is a great seinen love story. If adult romance with a good happy ending suits you. I definitely recommend you read Hetakoi.