Breach Security (セキュリティ突破, Sekyuriti Toppa?), Reach Mako Storage (魔晄だまりを目指す, Makōdamari o Mezasu?, lit. Head for the Mako Reservoir), Follow Jessie (ジェシーに続け, Jeshī ni Tsuzuke?), and Set the Charge are quests in Final Fantasy VII Remake, taking place in Mako Reactor 1 during Chapter 1, "The Destruction of Mako Reactor 1". Having infiltrated the Mako Reactor 1, Cloud Strife, hired by Barret Wallace and Avalanche, fight through Shinra Electric Power Company defenses in order to destroy the reactor. At the end, they encounter the Scorpion Sentinel.
Walkthrough[]
Breach Security[]
Upon entering the reactor, a cutscene will commence. After this, talk to Biggs, who will hack the door to the first room where Cloud proceeds first. Four security officers will close the door behind Cloud, commencing a battle. These enemies can be defeated quickly with normal attacks. After defeating them, talk to Jessie, and she will open the door. A chest can be open on the top-left corner of the room to obtain a phoenix down.
Interact with the button on the right of the elevator to begin a scene, and Cloud will enter the elevator up to the Utility Access. Once reaching it, the player gains control of Barret Wallace. Barret has ranged attacks with his gun, which will fire in rapid-fire before briefly overheating to fire again. but less area of effect than Cloud's sword. In addition to his attacks, he has the 
ability Overcharge, which deals heavy damage and increases stagger. Once being used, it is on a cooldown that can be shortened by pressing Charge. To maximize use of Barret, the player should press Charge immediately after the normal attack gun overheats, bringing Overcharge online more quickly and not wasting this moment. Barret also has the ATB commands Steelskin, which temporarily reduces damage taken and how easily he is interrupted, and Focused Shot, which unleashes a burst of energy and increases an enemy's stagger. Barret also has the spell 
Thunder, dealing Lightning damage which the robotic enemies are weak to, and Cure which restores HP.
Sentry Rays are ranged enemies that can only be targeted by Barret, and if not careful, the party will sustain damage from their lasers. Barret can make short work of the Sentry Rays using Overcharge, normal attacks, and Focused Shot. Monodrives are also fought, but can be destroyed by Cloud or Barret quickly.
Reach Mako Storage[]
After the battle, the player must head down the first staircase and meet up with Jessie. This quest then extends across the following quests.
Follow Jessie[]
Mako Reactor 1 - B4.
Jessie will then inform Cloud of the laser defense system. Run through the lasers before they activate in order to stop taking damage. After passing through the last laser set, a staircase leads down to another floor with more lasers. At the end of it, a chest can be opened containing two potions, and a staircase leads down further to a large floor.
At the bottom of the floor, a sweeper is located in front of the main door, though behind the staircase is a bottle of ether contained in a treasure chest. The sweeper when engaged is a much tougher opponent than those previously encountered, but is weak to lightning-based attacks. Use Barret's Thunder and Overcharge, and Cloud's Focused Thrust, to stagger it, then lay into it with Thunder from Barret or Braver from Cloud. After defeating it, heal using potions or Barret's Cure, then catch up with Jessie, who opens the door then leads the two through a hallway to the scaffolding above the core.
Set the Charge[]
Fighting the Scorpion Sentinel.
Take the ladder leading left down to the first metal platform. At its furthest end is a chest containing a tuft of phoenix down. Head down the stairs to the right, and then down the ladder to the next platform. Three Monodrives and one Sentry Ray are fought here; as before, Barret should destroy the Sentry Ray while Cloud can defeat the Monodrives. Head right down a set of stairs, and defeat the four Monodrives at the end located by the chest containing another bottle of ether. Next, head down the ladder onto the main core area.
Upon reaching the core, a cutscene will commence, followed by the choice to either set the bomb at 20 minutes or 30 minutes. 20 minutes should be more than enough time to escape the reactor, as the timer does not start until after the following boss battle.
At the end of the cutscene, the Scorpion Sentinel appears, the first boss. In the first stage of this fight, switch frequently between Cloud and Barret to unlock their ATB commands and use Focused Thrust and Thunder respectively to raise the boss' stagger gauge, switching to Barret when it latches onto the wall. Cloud can remain in Punisher Mode and guard against its attacks up close. When the boss staggers, unleash Limit attacks, Thunder, and Braver.
When the boss engages its barrier, focus on its Field Generator with Cloud, while Barret uses his ATB commands to heal. The second stage of the fight is mostly the same, but while the boss is charging its Tail Laser, Cloud should hide behind debris, while Barret can continue to shoot if he is standing at sufficient distance. In the final stage, destroy the two legs to stop the boss from auto-repairing, and the fight should end.
Once the Scorpion Sentinel is destroyed, the chapter continues in Escape from the Reactor.
Hard mode tips[]
Triple Slash can be used effectively against many enemies, and Cloud can equip 
First Strike Materia to open many battles with this ability. Barret will use much the same moves as on a normal playthrough against most enemies. Against the sweeper, equipping Cloud or Barret with 
Lightning Materia and 
Elemental Materia, and using a mix of abilities such as Focused Thrust and Focused Shot to pressure and stagger it, is best to take it down; casting spells should be avoided early on. The timer for the bomb can only be set as twenty minutes.
Defeating Scorpion Sentinel will award Barret with Sharpshooter's Companion Vol. IV. Its attacks hit a lot harder, and are even more crucial to guard against its attacks. Scorpion Sentinel's Tail Laser attack, unlike before, can hit Barret from a range, and will hit twice. This means Barret will have to get behind debris as well, and that both characters will have to run behind one piece of debris, then immediately hide behind the next, to avoid damage.
As before, Barret can use Focused Shot (especially when charged with two ATB bars) and Cloud can use Focused Strike to build up its stagger gauge Steadfast Block Materia can be very useful to guard against its damage, and Cloud can make great use of Counterstance to both reduce damage from its attacks and get in his own. Barret can use Lifesaver also to spread damage a bit, as Cloud will receive most damage since he is in melee range. Lightning materia can be useful when paired with elemental materia on a weapon, or when paired with HP Absorption Materia to heal the caster while also dealing damage.