TL;DR: Assign one "host / route owner" to hold NPC tasks, special bait, boss drops and hand-ins. Store copy says "1-4 players"; a later patch supports 8 β trust the patch notes. Black screen on join? Troubleshoot network/files before blaming the walkthrough.
Talks to NPCs, holds special bait, triggers bosses, collects drops, completes hand-ins. Don't hand route items to everyone.
Controls boat travel, waits for hand-in confirmation. Don't leave the island before the owner is done.
Brings reliable weapon/tool upgrades for boss fights. Don't open fights before the group is ready.
Farms and sells normal safe catches. Don't sell unknown quest items.
Tracks fish, bait, achievements, patch notes. Don't mix optional cleanup into urgent progression.
How to Fish is chaotic on purpose, but route items are fragile in a chaotic group. Ten seconds agreeing on roles saves twenty minutes guessing where the Carrot, Tuna, or a boss drop went.
If a step works for one player but not another, assume state or ownership before assuming the guide is wrong. Let the host re-read dialogue and carry the key item.
Start with two players, clear the Lighthouse, confirm the Spider Crab hand-in, then expand. Black screens, performance, and ownership problems become much easier to isolate.
How many players? Store says "1-4"; patch supports 8 β trust patch notes.
Who holds boss drops? Host or route owner, until hand-in.
Friend can trigger something I can't? They or the host may own the active route state or item.
Black screen on join? Open the black-screen checklist and test safe lobby steps first.
Co-op isn't "press together" β it's "one person sees it through". Lock route items on the host and let everyone else make chaos. That's the correct way to play this game multiplayer.
Before joining, read controls; for item protection see quest items & NPCs.