|Lol, I agree with you. I like Suwa's personality and how he's cheering on Kakeru and Naho's relationship.
However, I can't shake the feeling that that's not all there is to it. Relationships and emotions and the like are never as simple as A + B = C. Call me a pessimist, but it's kind of suspicious that Suwa is cheering them on so adamantly. Whenever I see a person (Suwa), who likes someone (Naho), promoting the relationship of that person with another person (Kakeru), it makes me suspicious. They always have some ulterior motive for what they're doing.
Spoiler (mouse over to view)
I keep seeing this on the internet everywhere, but it isn't true; Suwa never says that he got a letter from himself. He just asks if Naho got a letter. You can infer that he did, but for all we know he could either be referring to something else, or he could be saying that because Azu, Taka, and/or Hagita each received one.
But at the same time, I get the feeling that if Suwa did receive a letter, he knows that his future self will end up with Naho, and he's willing to make the sacrifice.
If we're going along with the parallel world theory, that would be why I'm skeptical of his actions. But with the single world/past/future theory, Suwa knows he'll end up with Naho in the end. Which would make me rage.
So it's probably that, or he knows that it might not work out with Kakeru + Naho, or that Kakeru doesn't even like Naho...
Unfortunately, but also fortunately, with series like these, you can't predict anything. Who knows what will happen.
I'm certainly looking forward to the next chapter.