LINKS UPDATED (05/05/2019)
This is truly the ultimate guide, you can't go wrong with this... If you have any problem though, feel free to ask (i'm sure you can solve 99% of the issues by carefully reading/using the description though); you'll also find a bunch of useful comments from many kind users below. In fact, you too can contribute! The only thing you have to do is simply finding whatever of those awful errors that are present in the installation process. If you manage to solve them, don't hesitate to report here; this way i can stick it for others to see. PS: The images presented in the video can be considered obsolete, at least if you don't mind playing an older version. If that's the case, the links labeled with a '(*)' are the ones i've personally used. Don't worry though, this description will be a repository even for the user who wants all the things, recent or not.
(INSTRUCTIONS: The links below are shrunk; you just need to wait 5 seconds and click the yellow button at the top right section of your screen).
IF YOU LIKE THE GAME, BUY IT!
あなたがこのゲームが好きなら, それを購入!!
Official Website of the game
http://destyy.com/wMdbVI
BASE GAME DOWNLOAD
Mirror 1: Mega (*)
http://destyy.com/wMdnyh
Mirror 2: Sukebei, Torrent (+ DLCs Pack)
http://destyy.com/wMdnpd
Mirror 3: (Recommended link): Magnet (you'll still need a .torrent downloader)
http://destyy.com/wMdnn6
Mirror 4: (another) Torrent
http://destyy.com/wMdn06
EXPANSIONS DOWNLOAD ('Act 2' / 'Act 3')
From browser: http://destyy.com/wMd9WU
(scroll all the way down or just use CTRL+F with the keyword 'act')
From torrent: ACT 1: http://destyy.com/wMdnn6
ACT 2: http://destyy.com/wMdnYr
ACT 3: http://destyy.com/wMdmuF
DLCs & UPDATES
(Use the 1st mirror to update the game. The link will re-direct you to the official website).
Mirror 1: Kiss Website (for updates)
http://destyy.com/wMdmmQ
Mirror 2: Pastebin (For DLCs, browser download)
http://destyy.com/wMd9WU
Mirror 3: Sukebei (For DLCs, torrent download)
http://destyy.com/wMd9nD
Mirror 4: Magnet (.torrent downloader required)
http://destyy.com/wMdQn0
Mirror 5: Mega (*)
http://destyy.com/wMdnfL
DLC AUTO-INSTALLER
Mirror 1: http://destyy.com/wMdQUK
HF PATCH (Mods, uncensor and translation)
WARNING: HF-Patch is, as other users said, obsolete. Use Sybaris instead (if you want to play older versions of the game you can still stick to this one though)
Mirror 1: Mega (*)
http://destyy.com/wMdmLo
SYBARIS
(HF-Patch may be obsolete by now, at least if you want all the latest things that the game has to offer. If that's the case, just drag and drop the contents of this folder into your game directory)
Mirror 1: Mega
http://destyy.com/wMd9R2
SYBARIS II (NoctSoul's Sybaris)
(Use this one if the other one doesn't work for you)
Mirror 1: CM3D2 Website
http://destyy.com/wMd9V9
AUTO-TRANSLATE
This plugin roughly translates the game. Probably better than the incomplete version of HF-Patch.
Mirror 1: Github
http://destyy.com/wMdQQN
YetAnotherTranslator - YAT (An alternative to Auto-Translate)
Mirror 1: Github
http://destyy.com/wMd9Ap
YAT Fixes
Mirror 1: Github
http://destyy.com/wMdQQN
UI Translation Patch
Mirror 1: Google Drive
http://destyy.com/wMd9SS
=================================================
(very) USEFUL LINKS
Anime Characters Presets
(If you don't find the one you wanted, just select another mirror)
Mirror 1: http://destyy.com/wMdQ8t
Mirror 2: http://destyy.com/wMdWnx
Mirror 3: http://destyy.com/wMdWj5
Mirror 4: http://destyy.com/wMdWws
Virtual Reality (VR) Patch
http://destyy.com/wMf0Yq
Huge link(s) repos with mods, DLCs, cheats, base game, expansions, translations and other utilities (You can also use these links if something is unavailable)
Mirror 1: http://destyy.com/wMd9vk
Mirror 2: http://destyy.com/wMdW2k
Mirror 3: http://destyy.com/wMdWHQ
Step by Step guide on installation process
(this will surely come in handy)
http://destyy.com/wMd91d
CM3D2 Wiki: Technical Help (Step by step guide, errors etc.)
http://destyy.com/wMdmj8
If you ask your questions HERE you'll surely
increase the probabilities that someone will help you.
http://destyy.com/wMdQGJ
Updating game with new DLCs
http://destyy.com/wMdmd1
Guide to installing MultipleMaids, Sybaris, and Reipatcher
http://destyy.com/wMdQyd
Older Updates
http://destyy.com/wMdQLg
NTLEA; Official Website
http://destyy.com/wMdQd2
AppLocale; Official Website
(If you want to be on the safe side while installing, use this in order to fake your PC as a japanese locale one. Sometimes the game won't work if you don't use this mechanism).
http://destyy.com/wMdQko
Daemon Tools LITE; Official Website
http://destyy.com/wMdQvr
uTorrent; Official Website
http://destyy.com/wMdQJV