Kouchou-sensei to Kujira

Both are very short, few minute long movies. Both feature whale, but while in Kujira it´s about fighting whale, in Man & Whale it´s about saving it. 

Both have men and both have whales. 

While Man and Whale is a Greenpeace commercial about saving whales, and Push is a social satire on consumerism and nuclear warfare, essentially both of them are shorts about preserving our planet that come from very talented directors - Koji Yamamura and Osamu Tezuka respectively. So, if you're interested in the topic, check them both. 

Similar mood and general feeling. A bit of surrealism and nostalgic.