lilacrose.dev

Paper Lily Ch.1 / Co-op Mod

fan-made, unofficial, free
v0.2.4 alpha

I wanted to play Paper Lily with a friend but there's no multiplayer, so I added it. This mod patches your existing Steam copy to let two people play through the whole game together online.

One person hosts and gets a short code to share. The other types it in and joins. You can start fresh or load an existing save — both players will be in the same spot. Room transitions wait for both of you, and the boss fight at the end works for both players too.

I run a small relay server to handle the connection so neither player needs to forward ports. It doesn't log anything, it just shuffles packets.

Download

Windows paperlily_coop_setup.exe Linux paperlily_coop_installer_linux

needs Paper Lily - Chapter 1 installed through Steam - re-run any time to update to the latest version

Installing

Windows
Linux
  1. 1
    Make sure you have Paper Lily - Chapter 1 installed via Steam.
  2. 2
    Download and run paperlily_coop_setup.exe. It'll find your game on its own, and if it can't, just paste in the folder path.
  3. 3
    It backs up your original PaperLilyCh1.exe before touching anything, then downloads and applies the patch.
  4. 4
    Launch from Steam like normal. Co-op will be in the main menu.
  1. 1
    Install Paper Lily - Chapter 1 through Steam (it runs via Proton). Also grab xdelta3 from your package manager if you don't have it.
  2. 2
    Download paperlily_coop_installer_linux, then: chmod +x paperlily_coop_installer_linux && ./paperlily_coop_installer_linux
  3. 3
    Same deal - it finds your game, backs up the original, patches it.
  4. 4
    Launch through Steam as normal. Proton handles running the patched exe.

Playing

  1. 1
    One person opens the game and picks Co-op → Create Game. You'll get a 4-letter code.
  2. 2
    Your friend picks Co-op → Join Game and types the code.
  3. 3
    The host chooses to start a new game or load a save. Both players start from the same place.
  4. 4
    When you want to leave a room, both players need to walk to an exit. Hit Cancel if you're not done yet and want to keep exploring.

Changelog

v0.2.4 — June 2026
  • fixed room transition confirmation overlay never appearing — co-op transition now triggers on any non-cutscene move command while connected, not just events with an explicit event_start flag
v0.2.3 — June 2026
  • fixed co-op not activating at Ch1_Home_Exterior_Front — SignalCoopReady now fires even when a cutscene is running on room entry
  • player name now saves between sessions and mod updates
  • debug log now shows localReady and partnerReady flags on each room change
v0.2.2 — June 2026
  • co-op now activates when both players first reach Ch1_Home_Exterior_Front — each player plays through the intro independently until that point
  • fixed seeing each other when co-op activates in the same room — no longer triggers a room reload
  • debug overlay (F3) is now hidden by default
v0.2.1e — June 2026
  • fixed debug terminal: log file now activates when pre-created by the Steam launch option, since Proton doesn't forward command-line args to the EXE
v0.2.1d — June 2026
  • fixed debug terminal log not being created — now uses STEAM_COMPAT_DATA_PATH which is the same path on both the host and inside the Proton container
v0.2.1c — June 2026
  • added in-game co-op debug overlay (shows room, coop state, last event) — toggle with F3 during a co-op session
  • added --debug-terminal Steam launch option support — writes live debug output to /tmp/paperlily_debug.log
v0.2.1b — June 2026
  • fixed both players not seeing each other after the intro — co-op now activates the first time each player gets movement control, not at a save point
  • fixed client getting stuck on title screen when host loads a save — client now syncs from host instead of loading independently
v0.2.1a — June 2026
  • both players now play through the intro independently — no more getting yanked back to the beginning
  • co-op sync starts automatically once both players reach the first checkpoint
  • talking to an NPC no longer shows the dialogue box on both screens
  • room transitions now properly wait for both players again (was bypassed in v0.2.0)
  • being in a cutscene no longer freezes the other player's game
  • fixed "Start New Game" not appearing in the lobby after returning from a previous session
v0.2.0 — June 2026
  • player names now displayed below each player in-game using the game font
  • co-op saves are now separate from singleplayer saves (prefixed coop_)
  • when one player saves, the save is automatically shared with their partner
  • on death in co-op, both players respawn instantly from the last shared checkpoint (no death screen)
  • fixed client freezing and crashing mid-session (CleanScreenLayer instead of Clean on room sync)
  • fixed reconnect bug — starting a new session after quitting now works correctly
v0.1.8a — June 2026
  • fixed non-host getting stuck on the flashing lights warning screen at new game start
  • added player names — set your name in the lobby and see your partner's name
  • removed X and Z from session codes (they're action buttons, not good for typing)
  • sessions now properly close when both players quit to main menu
v0.1.7a — June 2026
  • added OK button to room transition overlay — partner can now confirm directly instead of walking to an exit
  • remote player now appears in bathroom mirror reflections
  • death is now synced to partner — they see a waiting message while you respawn
  • ending/credits screen now shows for both players
  • client requests state resync from host after respawning
v0.1.6a — June 2026
  • fixed remote player showing sliding animation instead of walking
  • fixed black screen when host transitions rooms while client has a menu open
  • fixed room transitions: client was sometimes changing rooms independently of the host
  • fixed loading spinner persisting after a failed room transition
v0.1.5b — June 2026
  • fixed Z and X keys being consumed as confirm/cancel when typing the join code
  • fixed dialogue getting permanently stuck after a network room change
  • fixed fishing minigame starting on the non-triggering player's screen

Uninstalling

Run the installer again with --uninstall, or just delete PaperLilyCh1_original.exe and do a Steam file verify and it'll put the original back.

Fan-made, not affiliated with Leef6010. The installer only patches your own copy of the game, it doesn't bundle any game files. If something breaks or you run into a bug, feel free to reach out.