Go to the Ramen after the fifth day. There you meet Orochimaru. As it turns out, you ended up in this world because of his experiments. He’s willing to share with information about that experiment in exchange for a small favor.
After talking to Orochimaru, go home, wait for next day and then go to the balcony. There you will find a scroll with information about the location you need to get in: See you near the building behind the hospital… .Go to that place and there you’ll be met by Karin who will guide you through the labyrinth into a lair.
Orochimaru agrees to give you access to information once you get Naruto’s blood for him.
In order to get that blood, go to the flower shop to Ino. Talk to her. If her trust to you is above 14, you will have an option to ask her to get Naruto’s blood for you.
Go back to her in 3 days and ask about this task. If you come earlier, you will just lower her mood and trust points. She gives you two vials of Naturo’s blood. After giving you the vials, she will ask you whether you trust her.
Choice of answers:
After that go to the building behind the hospital to Orochimaru. At the entrance, you’ll be met by Karin who will guide you through the labyrinth. After giving the blood, Karin will guide you to the laboratory where you can examine the experiment’s materials. However, you can’t understand a word what’s written in those materials and that’s where Karin will offer to help you in exchange for help with other things. But she’s busy at the moment so you’ll have to wait a few days.
In three days, you’ll wake up in the morning because you hear someone scratching on your balcony. Go out on the balcony and find a scroll from Karin. She says that she took care of her business and she it's ready to help you. From now on, Karin won’t wait for you at the entrance anymore and that’s why the scroll contains the instructions of how to get through the labyrinth Up-Left-Up-Left-Left-Down.
Already with the instructions, we go to the laboratory and talk with Karin. She will gives us 50 sheets from Orochimaru's experiment. We read them at home and the next day we go to the laboratory to see Karin. We repeat this action for 3 more times. When the time comes for the third investigation, Karin may not be in the laboratory, so that to advance in the main branch and make Karin appears there, you need to go through the Tenten's branch until the moment when you need to buy vases from Karin in the forest.
To start the fourth investigation you must have at least one vase in inventory. Karin will ask you to pick mushrooms in the forest. In total, you need to collect 8 mushrooms, after which we are automatically transferred to the laboratory, where we accidentally spy on how Karin changes clothes.