A quick guide to all secret events and scenes that you can easly miss during the gameplay. Minor spoilers ahead!
Intro
In this guide i'll be showing how to unlock every secret scenes and events! The scenes usually occurs during the Free Time or Daily Life, in most cases you'll need an Specific Item. The item you can get in the MonoMono Yachine using Monocoins. The Mono Yachine is located on a palm tree on the 1st Island's Beach.
Note that: In each game there are different ways to earn Monocoins, in Goodbye Disapir you can earn them by Collecting Hidden Monokumas which grant 10 coins for each one you find, after Completing Class Trials and by Raising Pets in the minigame on the e-Handbook.
A really useful tip is to make a save before spending your Monocoins in the Mono Yachine and if you don’t get the item, just reload and do it again and again and again... until you finally get it.
In Danganronpa 2: Goodbye Dispair we have 6 special scenes in total, they can be triggered once you have theitem in your inventory and sometimes you'll need to talk to someone before the Free Time Event.
I'm also assuming that you have the following items in your inventory, so make sure you have them before trying to unlock the scenes!
Warning! Minor spoilers ahead!
I won't give much details about the scenes or what leads to it. However i will just drop a spoiler image down below, so be careful if you don't want any spoilers...
Vending Machine
A really cool feature that we have in this game is the Vending Machine located in the Rocketpunch Market, which you can purchase any item of your desire.
The cost of the items for the secret scenes is 50 Monocoins each.
If you have any questions on how to access the Vending Machine you can check on this video!
Chapter 1
A sword for display purposes. The sheath has a scratch on it, and the gold foil near the hilt is scraped off. It doesn't look very valuable...
Having this item in your inventory you must speak to Kazuichi Soda before meeting Byakuya Togami to Jabberwock Park, then the event will happen during the next free time!
Part 2
A fashion magazine for teenage girls and women in their twenties. Its articles about topics such as the latest fashion trends, cooking techniques, and tips for appearing more feminine have made it extremely popular.
You must speak to Mahiru Koizumi before going to the restaurant in the morning after Monokuma presents a motive like the first one, it will also happen during the next free time!
Chapter 2
A huge nut that can't be found in nature. It's said to exist within a man's heart. It's said that consuming this will increase your power to pursue romance.
Right at the start of the chapter, speak to Mahiru Koizumi before exploring the second island. The event will then happen when you speak to Mahiru.
P.S: This is considered a NSFW scene.
Chapter 3
A cheaply made camera. Due to its poor quality, its photos are sometimes out of focus or have weird coloration. Oddly enough, that has actually made it more popular.
Talk to Hiyoko Saionji on the morning after exploring the third island. The event will then happen in the next Free Time.
Part 2
The debut single of the boy band, Black Cherry. This song became a huge hit due to its rhythmic beat and catchy lyrics about summer.
Talk to Ibuki Mioda on the morning after exploring the third island. The event will then happen after the next Free Time just before the day is over.
Part 3
A manga about a boy named Taro who fights using RC cars. Children across Japan cried when Taro said this line in the final chapter: "Adults will never understand! A goal is still a goal, even if it's a reverse run!"
Talk to Kazuichi Soda right after everyone visits Fuyuhiko Kuzuryu in the hospital.
Note that you must talk to Kazuichi Soda before talking to anyone else, otherwise the story will continue and you will miss the scene.
Source: https://gameplay.tips/guides/5726-danganronpa-2-goodbye-despair.html