'Discover a glimpse of Japan' is correct English. I wouldn't call it a pleonasm. A pleonasm is defined as
'the use of more words than are necessary to convey meaning (e.g., see with one's eyes ), either as a fault of style or for emphasis.'
In this case, we could discover lots of different things about Japan. We could discover where it is, some facts about it, or something about the people. The clarification 'a glimpse of' tells us what we will discover about Japan, and is not redundant at all.