At some point, Japan decided that spaces were for losers, so when reading Japanese prose the mind operates like a regular expression engine, advancing as many characters as it can looking for a valid match, but not finding one, backtracking until matching a known word (even if the word is just one character). If you’ve been reading kanji since age five, your brain makes this happen automatically. If not, it makes you want to douse your Japanese textbook in gasoline, light it on fire, and launch whatever survives directly into the blazing hellfire of the sun. Yet another layer of difficulty in an already really, really difficult language.