In Hinduism, Manu is a title accorded the progenitor of mankind, first king to rule this earth, who saves mankind from the universal flood. He is honest which is why he is called "Satyavrata", or oath of truth.
Mahabharata says: "And Manu was endued with great wisdom and devoted to virtue. And he became the progenitor of a line. And in Manu's race have been born all human beings, who have, therefore, been called Manavas. And it is of Manu that all men including Brahmanas, Kshatriyas, and others have been descended, and are, therefore, all called Manavas. Subsequently, O monarch, the Brahmanas became united with the Kshatriyas. And those sons of Manu that were Brahmanas devoted themselves to the study of the Vedas. "The ten sons of Manu are known as Vena, Dhrishnu, Narishyan, Nabhaga, Ikshvaku, Karusha, Saryati, the eighth, a daughter named Ila, Prishadhru the ninth, and Nabhagarishta, the tenth. They all betook themselves to the practices of Kshatriyas. Besides these, Manu had fifty other sons on Earth. But we heard that they all perished, quarrelling with one another."
Krishna (कृष्ण in Devanagari, kṛṣṇa in IAST, pronounced [ˈkr̩ʂɳə] in classical Sanskrit) is a deity worshipped across many traditions of Hinduism. He is usually depicted as a young cowherd boy playing a flute (as in the Bhagavata Purana) or a youthful prince giving philosophical direction (as in the Bhagavad Gita).
Most commonly within Hinduism, Krishna is worshipped as an avatar of Vishnu (Vishnu is considered the Supreme God by the Vaishnava schools). Within Gaudiya Vaishnavism and the Nimbarka Sampradaya, Krishna is worshipped as the source of all other avatars (including Vishnu).
Krishna and the stories associated with him appear across a broad spectrum of Hindu philosophical and theological traditions. Though they sometimes differ in details reflecting the concerns of a particular tradition, some core features are shared by all. These include a divine incarnation, a pastoral childhood and youth, and life as a heroic warrior and teacher.