
That in regards to the ending, the way I see it, it's not so much heartbreak, than it is disappointment. It's his first ever "relationship." He doesn't know what that feeling is. He even literally asked "is this what heartbreak feels like?" No, it is not. Heartbreak is followed by depression. As someone who was rejected and dumped a few times already, I'd know the difference. In short, he wasn't that emotionally invested in Miki. That, again, is the way I see it.
...is it "Love Sick Dog" as in "dog who is under love sickness" or "Love Sick Dog" as in "someone that love sick dogs"? /j
dog represents the white hair, so basically he is a dog who is needy for love
/j means joke
They actually both depicted as love sick dogs just in different ways,,, jooin is a dog as well in later chapters