Between Yesterday and Tomorrow (1954)

Original title: 昨日と明日の間

A young man hands in his notice at work and breaks up with his girlfriend in order to pursue his true nature and dream of shaping the world according to his own desires. Against all the odds, he manages to push through his business idea – the foundation of an airline. At the same time, his ex-girlfriend refuses to accept their separation and attempts to force her way back into his life by any means possible. He in turn feels attracted to a young woman, who turns out to be the wife of one of his airline investors and who has herself had a secret lover for several years.