Probably the toughest achievement nowadays, considering the lower population. Just figured I would try to help some other people out, people who may be in the same situation as me. 🙂
Complete the majority of the Journey with the same person, ascending together and returning to the beginning.
This in mind, here are some tips in how to get the achievement and complete the Journey.
Note: you can also check out the 100% achievement guide from here.
This is the underwater level right after the Sunken City/surfing section of the game. It is also the one before the beautiful temple section. Easiest to identify it is its dark color scheme, filled with blues, as well as it being the first area with the guardians in them. The reason I name off this area, is that this is the latest you can enter the Journey and complete it together with the same player, while still activating the achievement. The temple onward is considered to be too late to join up.
Tip Number 2: Test the Waters in Matchmaking!
Upon matchmaking with another player, sit with them for a bit, and see how they play. If they don’t wait up or try speed-running, it may be difficult to complete the rest of the game with them. If they act impatient (or if you are the impatient one), they will also be a less than ideal fit. Keep in mind, if you like the game enough, you could still try running with these kinds of players, but it is not recommended. The best person would likely be a newer, inexperienced player that you can shepherd. That way, if patient enough, you can help each other out. They get a friend to the top, and you get the achievement!
Tip Number 3: Use Discord to Play With Friends!
The easiest idea? Match-make with someone you know! That way, you can communicate, joke around, and have a lil fun. Just make sure to still start at the passage. For those without friends who play Journey, I am opening up a tiny discord server to more easily LFG. Feel free to join, and hopefully people will help you out!.
Thanks to Dirty_Rob for his great guide, all credit to his effort. you can also read the original guide from Steam Community. enjoy the game.