Well, it was also because of his boyfriend that Hanamine wanted to go as well. He wanted to be someone who could stand beside his boyfriend proudly. Most likely he wanted to make the foundation of their relationship strong no matter if their parents opposed their relationship going forward.
Not wanting your lover to go abroad suddenly for their studies is normal, especially since they've been together since child and have to separate for many years.. in the end it's still the uke's decision but even if seme wants to break up it make sense, it's quite rational of him already.
I"m glad he didn't yield to the seme's selfish demands and persued his dream, you don't compromise your future under the guise of love.