What do Buddhist teachingssay about feelings of guilt?
Guilt is not really found in Buddhism. Buddhism teaches us to take responsibility for our thoughts, words and actions. If we make our decisions with the best of our abilities, then as long as we also take responsibility for those decisions, then there is no guilt.
Culturally, many Buddhists and especially Japanese Buddhists live in a society that is strongly biased by shame. One does not do things that bring shame to the family or to the village or to the group. Shame can function much like guilt, but one should know the difference.