In fact, he wants to burst into tears, holding the hands of his son, but he cries only in his heart without directly showing his sorrow, suppressing his own feelings; this rigidness of ancient samurai rather makes the audience feel sorry for the parents and children.
本当なら息子と手を取り合って、わーっと泣きたい心境なのですが、その悲しみを露骨に出さず涙を抑えて心で泣く、大義のために私情を殺すという古武士の硬骨を見せることで、逆に親子の哀れさがお客様に伝わるのです。