The main gang insists on befriending Kakeru right on the get go, despite not knowing if the latter, who originates from Tokyo, is a City Mouse or not.
Azu's fetish is wanting to see Hagita trades his glasses with contacts for good. In the future, he does exactly that.
All of Naho and Kakeru's heart-to-heart scenes, frankly, particularly when he helps heal her foot injury after the baseball match, as that's the time when she falls in love with him.
Although a Love Triangle exists, there is little to no drama present (unlike a great many shojo manga), and the trio keep their friendship through and through. This is thanks largely in part to Suwa, the ultimate definition of Nice Guy, who ships Naho and Kakeru despite being in love with the former.
Heck, future Suwa's biggest regret (and why he advises his past self to give Kakeru a chance to woo Naho) is not be able to see Naho and Kakeru end up together. That outcome outweighs everything, including his own marriage to Naho.
Related to the love triangle above, both Suwa and Kakeru technically win over Naho's heart thanks to the existence of multiple timelines. No guy left behind here.
Kakeru's self-described reward for the relay race win is kissing Naho.
Naho's love confession to Kakeru the day before Valentine. Of course, he accepts it; he (and the others, and the readers as well) has been dying to do it for long.
The reason Kakeru's mother committed suicide is not because she thought that Kakeru didn't care for her. No, she did it so he could move on with his friends and be spared of having such a terrible mother, as she described herself. Unfortunately, it didn't go as well as she expected.
Kakeru is discouraged from committing suicide when he realizes that by doing so, he would never be able to be with his friends again. Cue his and the gang's Tears of Joy.
One of the questions Kakeru posed for his future self is whether he is married to Naho or not. For those curious of the answer, yes, he is. With a son to boot.
Saving Kakeru turns out to yield many more benefits than, well, just see him alive and well. In the original future, there's no indication that Azu and Hagita are dating other than some subtexts, but in the alternate future, it's fully confirmed.
