@AbuHajaar Why would Japan not know of HRE and why would it be hard to get there? The 16th-17th centuries were the times European missionaries (like Francis Xavier) from Spain and Portugal frequently travelled to Sengoku Era Japan to spread Christianity. Some daimyos either became Christians or tolerated the missionaries, at least until the Tokugawa shogunate closed Japan off to the outside world during the Edo period, and later persecuted Japanese Christians (one notable event being the Shimbara Rebellion under Shirou Amakusa).
But more to the point, Japanese did come to Europe: Bernardo the Japanese was a Japanese Christian and the first Japanese to set foot in Europe in 1552-53. Later, Japan sent two diplomatic missions to Europe, its kings and its Pope: the Tenshō embassy in 1582 and another led by Hasekura Tsunenaga from 1613 to 1620. All those instances taking place before or at the start of the 30 Years' War, so a Japanese ending up there is really not that far fetched.
The pre-industrial world was way more interconnected than our popular culture would like to make us think, so always check before thinking something couldn't have possibly happened in the past or they lacked more knowledge than they actually did. A Japanese in Europe is mild stuff: if that surprises you, the wild stuff like an African samurai is going to blow your mind.