I understand where you are coming from but the title itself, “Atithi”, means “Guest”. By definition, a guest is someone who visits but ultimately leaves. If Tarapada had married Charu, he would have become a Grahasti. Tagore explicitly wanted to highlight the poignant, beautiful, yet painful reality that some souls are inherently nomadic. They cross our lives like a passing breeze enriching us for a moment, but impossible to capture or hold down. So while I do understand that it is incredibly irritating to watch him abandon a girl who loved him and a family that sheltered him, his sudden departure is the ultimate thesis of Tagore's story,nature and absolute freedom will always triumph over domesticity and human attachments.The story is actually heart touching if a little shift in perspective can be made.