Out of interest, what prompted you to make such a trip? When I was 18 (granted this was only a couple of years ago) all I managed to do was stay with a host family for a few weeks in Japan :)
To be honest, after a pretty lackadaisical first year of college I wanted to do something a bit more extreme. So naturally I dropped out and started looking at Pilgrimage trails. I didn’t really understand much of the historical and spiritual significance of the Shikoku trail until I actually started it and spoke with other pilgrims. The experience, at least at the beginning, was more about taking a completely divergent turn and diving into a culture that had fascinated me for years. That said, if you want to go back, its a surprisingly affordable endeavor if you can clear 4-6 weeks.