Raphael Hythloday is a smart, smart guy, but he's bored with the regular old day-to-day and disenchanted with the political corruption and economic inequality of Europe. Luckily for him, there's lots of exploring going on, so he joins a ship, takes his books, and sails the world.
Hythloday is completely taken with this wonderful island of Utopia that he finds. He admires their customs, government, and legal system, particularly because they are all so different from what he knows in Europe. They welcome him openly and eagerly read the many books he has with him. He likes it there so much he stays for five years.
Since Utopia doesn't exactly fit with your typical "Voyage and Return" story—although it is playing around with that narrative model—Hythloday's "frustration stage" is a bit unusual. Instead of becoming frustrated with life in Utopia, the longer he stays in Utopia the more frustrated he becomes with what he knows is going on in Europe.
For Hythloday, this aspect seems less a particular stage than a general attitude. Although he returns to Europe to teach people about Utopia, Hythloday seems perpetually pessimistic that Europe and European governments are capable of being changed. At times, this outlook seems so dire, you wonder if Hythloday is capable of being happy anywhere other than Utopia.
Well, for poor Hythloday, it's really quite the opposite. He voluntarily leaves Utopia in order to return to Europe and share with other Europeans all that he's learned about Utopia. As his tone and general outlook suggest, Hythloday seems far from thrilled to be back in Europe and would much rather never have returned from Utopia.