Magi: Tensho Keno Shonen Shisetsu

Alessandro Valignano is an Italian Jesuit missionary who wants to spread Catholicism in Japan. He comes up with the idea to build seminaries all around Japan and to select excellent students from the seminaries to meet the Pope in Vatican City. Four boys are selected: Mancio Ito, Juliao Nakaura, Martinao Hara and Miguel Chijiwa. They travel to Europe to meet the Pope. During this time they face hardships.
(Source: AsianWiki)