This is story related but can be missed. After you go to warehouse 8 in New Yokosuka Harbor and learn of another warehouse 8 in Old Yokosuka Harbor, you (Ryo) must go there. Backtrack and take a right just before the entrance of New Yokosuka Harbor. In other words, do not exit. Take another right, following the big arrow on the ground. Take a left and follow the path until you reach the water. This is a night mission so you have to wait until after 8:00 PM.
When it is after 8:00 PM on the game clock in the upper right hand corner, proceed left along the water until you see a small gap leading to the old harbor. The road is mostly blocked. You can see the guard in the guard shack. Before you enter, make a save
: You are about to execute a part of the game where you do not have access to the
button and its save & exit features. This is a stealth sequence. Every time Ryo gets caught, the game advances a day and you restart at the entrance to the Yokosuka Old Harbor. The earliest you can attempt the sequence is 8 Dec 1986. You will need just under two more game weeks to finish the game playing as efficiently as possible. In the unlikely event you advance the game date beyond 3 April 1987, you will not be able to complete the game by 15 April 1987 and will get the bad ending to the game. Moreover, if you do not get this achievement by 15 April 1987, it will be missed as will all the other achievements you have not unlocked.
After you save, enter the Old Yokosuka Harbor. Be prepared for a
QTE. This is the first opportunity to fail the mission. In a short cut scene, Ryo bumps his head. Press
when prompted to catch a falling flashlight that would otherwise alert the guard. If you fail, a cut scene shows Ryo getting caught. He says he'll try the following day and the game date advances by a day. If you are caught, press
to exit the game since the game will not allow you to exit. Close the game from the XBox One Dashboard, restart it and continue from the save you made outside the harbor. This will be the technique to use any time you fail the upcoming stealth sequence so as to prevent the game from advancing its date.
Proceed forward. A short cut scene alerts you to patrolling guards and automatically has Ryo seek cover. You can see two guards. When the one walking towards Ryo turns right, follow him. After a few steps, you'll see some POL drums to your left. Press
to conceal Ryo behind them. The guard will turn around and go into an enclave to Ryo's right. He will come back and proceed on his patrol. As soon as he walks away from Ryo, follow after him. He will turn left just before warehouse 7. Follow a safe distance behind him. The next warehouse is number 8. Enter the door on the right hand side.
If at any point, Ryo is 'caught' before entering the warehouse door, dashboard as explained above and restart the game from the appropriate save point. Once you enter the warehouse, you will have access to
and can make an optional save. Once you are inside warehouse 8, you have successfully concluded the stealth section.
To the left front, as Ryo enters is a plate on a shelf. Use
to focus in on the plate (or
if you have changed the default). A cut scene shows Ryo being startled. He drops the plate and the achievement unlocks. Following the next sequence, the game will automatically return Ryo to his residence. The game resumes the morning after the night stealth sequence.