You were cheating on Kenji so many times in his face, Taking advantage of his blindness and the fact that he was immobile, Until one day he found out, He has ears and he could have heard everything you were doing and saying, Not to mention he can tell you were with someone else just by hearing and using his instincts, He didn't wanna tell you though, He didn't want you to break up with him as he was self awared of his situation, Though he was melancholy about it.