It may seem fickle, yes, but why keep loving someone in that way when you know they won't love you back? Hayakawa might have loved Tsuyoshi at first, but 8 years ago he cried because he was faced with the truth that he would never have him, that Hajizume now had Tsuyoshi's love. It was at that time that Kouki saw him crying and made his declaration to protect Hayakawa. From then, Hayakawa was able to watch Kouki grow and to fall in love with him during that time. I don't think it was an immediate "I love Tsuyoshi, no, now I love Kouki." Hayakawa had every right to move on, and he had 8 years to do it.
8 years is a long time. Love can develope in that time.
so damn agree with youuu
...for Hakayama. First he's in love with Tsuyoshi and when Hajizume gets caught making love to Tsuyoshi by Hakayama, he cries and decides to turn his affections towards Kouki. Fuck him. You can get mad at me for saying this but read the beginning of the series first.
1. Scandalous Seiryo University
2. Serenade
3. Tsuioku no Venus!
4. still...