At that time, Klein had a busy social life and the cafés, of course, often served as a backdrop to this activity. In such surroundings, he was no longer a mere observer, tagging along with Lisa to meet her friends. Café Mánes continued to be a favourite, but now that he was older, he would also frequent the students’ café on Na Zderaz, close to his old school. It was in 1938, at about the time of his school graduation ball, that he first met Hana Žantovská (1921–2004), who later became a noted Czech translator. They became close friends, though the relationship was not a romantic one. Hana first met Klein, ‘a very handsome young man’, as she describes him, at one of the cafés, and offers a very finely drawn portrait:

Through Hana, Klein met many of the young writers with whom she mixed, including the most famous of that young group, Jiří Orten, whose tragic death was to be immutably bound up with the fate of the Kleins during the war. Klein's knowledge of literature struck Hana immediately, observing that his understanding of it seemed to equal his expertise in music, that his friendliness and ability to connect with people was so evident, and that, in her words, ‘he knew how to share’.