He actually didn't planned to go to Seiso, but he took the entrance exam because it was close to his house. Later on he heard Ritsu playing the violin. After hearing about Ritsus goals and dreams he got a little envious and before he knew it he asked if he could have the chance to join the Orchestra Club and Ritsu told him he didn't know if he didn't heard his performance yet and after hearing that he entered Seiso.
Housei says to Daichi that he is "the weakest link" in the ensemble. Daichi did not think much on it nor did he continue fighting with Housei. Because he also thinks that he holds back the whole group, but Ritsu cheers him up saying he may have started the viola late but his aptitude, skill and feeling in it are well above average allowing him to be part of the ensemble.