Sima Yi

EX Weapon: Horsehair Whip
Weapon name and Skills: Royal Whip - Frost: 10, Awareness, Frenzy: 9, Vigor: 8
Stage: Pursuit at Wuzhang Plains
Requirements: Defeat 300 members of the Shu forces, including Zhao Zhi, Zhang Yi, and Du Rui.

There is a typo in the requirement for Zhang Yi it says Zhang Ni.

Achieving 300 KO is not hard with Sima Yis path. Zhang Yi and Du Rui will advance as soon as you defeat the 3 Shu officer in front of the castle, one of which is Zhao Zhi. Additionally you may want to defeat Xingcai before she reaches the Wei main camp.

Sima Shi

EX Weapon: Lightning Sword
Weapon name and Skills: Emperor's Light - Slash: 10, Jubilation: 9, Resolve, Survival: 8
Stage: Guanqiu Jian & Wen Qin's Rebellion
Requirements: Return to the Wei forces' main camp within 1 minute of Wen Yang's surprise attack.

Head to either indicated point on the map, then go back to the main camp after Wen Yang announces himself. Easiest 5th weapon to get in the game.

Sima Zhao

EX Weapon: Striking Sword
Weapon name and Skills: Sealant Blade - Slash: 10, Triumph: 9, Jolt: 9, Rigidity
Stage: Battle of Chengdu
Requirements: Defeat Guan Suo and Jiang Wei in Chengdu Castle within 7 minutes after Liu Shan temporarily withdraws.

The timer will start the moment Liu Shan withdraws from Luo Castle, Jiang Wei who is near him outside of the castle will not count to the requirement. Jiang Wei has to be inside the castle which is where he will go when you defeat him at Luo Castle.

Deng Ai

EX Weapon: Lance
Weapon name and Skills: Spear of Armageddon - Frost: 10, Barricade: 9, Flurry: 9, Protection: 8
Stage: Battle of Jiange
Requirements: Ensure the success of the decoy strategy and defeat Jiang Wei in the main camp within 8 minutes of starting the battle.

To ensure the success just defeat enemy officers marked on the map without approaching Shu Main Camp. Once Wen Yang has defeated Zhuge Zhan, defeat two officers in front of the Shu Main Camp to open the gates. After that the gates will close and Yueying will ambush you, defeat her, then Jiang Wei. The treasure will be visible once the map is expanded. The time limit is more than enough.

Wang Yuanji

EX Weapon: Throwing Knives
Weapon name and Skills: Rain Blades - Inferno: 10, Protection: 9, Aggression (Same Affinity = Attack up): 9, Jubilation: 8
Stage: Battle of Jianye
Requirements: Arrive at Sun Xiu's side within 8 minutes of Jianye Castle opening its gates.

Plenty of time using a properly tempered Throwing Knives. Make sure not to kill Sun Xiu before obtaining the weapon as he is the enemy commander.

Zhong Hui

EX Weapon: Flying Swords
Weapon name and Skills: Aerial Blade - Cyclone: 10, Fury, Triumph: 9, Flurry: 8
Stage: Battle of Taoyang
Requirements: Defeat Hu Ji, Liao Hua, and Zhang Yi within 5 minutes after Xiahou Ba begins withdrawing.

Complete each mission you're given and this will be done along the way. These three officers have a Red aura around them thus making them stronger than the regular generics.

Zhuge Dan

EX Weapon: Short Rod
Weapon name and Skills: Golden Might - Thunder: 10, Whirlwind: 9, Rigidity, Protection: 8
Stage: Battle of Hefei New Castle
Requirements: Lure out Zhuge Ke from the main camp within 5 minutes after the gates to New Hefei Castle open.

Follow every mission you're given and this will be done along the way.

Xiahou Ba

EX Weapon: Siege Spear
Weapon name and Skills: Spear of Conquest - Thunder: 10, Flurry: 9, Triumph: 9, Awareness
Stage: Capture of Chengdu
Requirements: Defeat Guan Suo and Guan Yinping before they can enter the Wei forces' main camp.

Defeating Jiang Wei will make Guan Suo and Guan Yinping appear near the Eastern garrison. At the start of the battle make your way to the Eastern garrison and defeat the enemy officer defending it to make rams to break down the castle gates, protect the ram till it breaks down the castle. One of your officers will be near the garrison to slow down Guan Suo and Guan Yinping.

Guo Huai

EX Weapon: Arm Cannon
Weapon name and Skills: Earthshaker - Venom: 10, Protection: 9, Induction: 9, Agility
Stage: Xiahou Ba's Journey
Requirements: Defeat all of the Shu officers along the way and successfully block the path twice within 8 minutes of starting the battle.

Follow the path completing the missions and you'll get this easily, you may want to save in the awkwardly placed platforming section.

Jia Chong

EX Weapon: Throwing Axes
Weapon name and Skills: Hidden Essence - Cyclone: 10, Survival: 9, Swiftness, Flurry: 8
Stage: Final Conflict at Chibi
Requirements: Seize the Coalition forces' ballista before they can be used to defeat a Wei officer.

First priority is to head to the indicated spot on the map, when you reach there an ambush will happen, your next task being taking out Zhang Yi to take control of the ballista. To give yourself more time defeat Liao Hua and the officers around where the ambush happened.

Wen Yang

EX Weapon: Javelin
Weapon name and Skills: Skycrusher - Thunder: 10, Jubilation: 9, Uplift: 9, Desperation
Stage: Defend Chengdu
Requirements: Defeat Meng Huo without the central garrison erupting in flames.

Simple task, deal with the three traitors in the castle. After this Jiang Wei will appear outside of the castle, defeat him. After this Meng Huo will appear in the center garrison rush towards him.

Zhang Chunhua

EX Weapon: Wired Gloves
Weapon name and Skills: Purple Fury - Slash: 10, Protection: 9, Vigor: 9, Fear: 9
Stage: Defeat the Rebels
Requirements: Defeat Zhong Chan and Zhong Yao within 5 minutes of starting the battle.

There is a typo in the requirement for Zhong Yao as it says Liu Yao who is long dead by this point in the timeline.

Immediately head to Zhong Chans location and defeat him. Make your way around to the East side of the map to Zhong Yao who is blocking the gate.