Samurai Warriors presents 15 legendary playable characters. At the beginning of the game there are 5 characters available: Yukimura Sanada, Hanzo Hattori, Oichi, Kenshin Uesugi, and Mitsuhide Akechi. The other 10 can be unlocked by completing the Story Mode using certain characters.
An interesting difference between Samurai Warriors and the Dynasty Warriors series is that the Japanese feudal clan system is less organized and more numerous than the Chinese kindom system. Whereas DW offered characters organized by kingdoms: Shu, Wu, and Wei - SW has the legendary heroes placed randomly.
An important note: The character selection bar will mold itself according to the order you unlock the characters. For example if you unlock Nobunaga before you unlock Kunoichi, Nobunaga's character block will appear before Kunoichis. In DW the characters had a set order in which they were presented, but SW lets you mold your own selection of legendary heroes. Keep this in mind when you decide to unlock characters so that you can customize your character selection bar to your liking.
Yukimura Sanada
Hanzo Hattori
Oichi
Kenshin Uesugi
Mitsuhide Akechi
Magoichi Saika ~ Beat Story Mode 1st time
Masamune Date ~ Beat Story Mode 2nd time
Shingen Takeda ~ Beat Story Mode with Yukimura Sanada
Keiji Maeda ~ Beat Story Mode with Kenshin Uesugi
Ranmaru Mori ~ Beat Story Mode with Mitsuhide Akechi
Okuni ~ Beat Story Mode with Keiji Maeda
Nouhime ~ Beat Story Mode with Ranmaru Mori
Goemon Ishikawa ~ Beat Story Mode with Okuni
Kunoichi ~ Beat Story Mode with Hanzo Hattori and Shingen Takeda
Nobunaga Oda ~ Beat Story Mode with Magoichi, Ranmaru, and Noh
You can see the order I unlocked my characters on my main page. You might want to try and group people together like having Shingen next to Kunoichi because they're both from the Takeda Clan or Noh and Nobunaga because they're married. I like having Magoichi next Masamune just because they're both kinda loners and are supposed to be the first two unlockable characters by default. Be aware the only way you can place them together is to beat Story Mode with Hanzo or Oichi first since they don't initially unlock any characters which will make Magoichi the only chararacter you unlock. I think Masamune Date will automatically appear before any other character you unlock on your second try, for example he'll appear before Keiji Maeda on the character selection bar if Kenshin is the second character you beat Story Mode with.
5th Weapons
Each character has a unique 5th weapon that can only be obtained by completing certain missions on a specific Story Mode stage on hard (or chaos?) difficulty.
Oichi
In "The Battle Anegawa" (Oichi's 3rd mission), complete all the assigned missions up to defeating the Mino Three. The key to getting the 5th weapon is to not let any of your generals die. If any of your generals are defeated, then the supply unit will not appear with the weapon. First Kill Tokugawa in the west. Also kill the other two enemy officers in the area to prevent them from routing your officers. Then you'll be instructed to stop Keiji Maeda. Kill Mitsuhide and Keiji at the center bridge. After defeating Keiji, Oichi will want to meet with Noh. Noh is located in the southeast, east of Hideyoshi in a camp with only a reserve captain visible. I suggest you defeat the other officers - one in front of Nobunaga's camp - and Hideyoshi before heading to Noh just to help out your officers. Go through the river pass adn defeat Noh and head back to Nobunaga's camp. Once you get close there will be an alert that there are three enemy ambush parties. It's the Mino Three and they will be after your base. You cannot let them enter the main camp. Defeat the officer closest to your camp and then finish off the other two. Once you defeat the Mino Three, a supply unit will appear from the south west and exit at the western exit. They shouldn't be too difficult to catch as long as you be careful not to accidently take any dead end passes.
The Sakura is a very cool 5th weapon. I don't have any complaints. It's lightning element, high attack and defense - where it counts. When attempting to get Oichi's 5th weapon, I suggest you use 2 players. It's easier to protect your officeres and wipe out enemy officers if there's twice the power. That and Oichi is a pretty weak character without her 5th weapon.
Kunoichi
In the "Rescue at Ueda Castle" infiltration (Kunoichi's 4th mission), reach Yukimura and Hanzo at the 5th sub-level with 30 minutes remaining on the timer. In other words reach the bottom floor within 5 minutes of starting the mission. The valuable item (and a weapon box that's always there) will appear in the left hut in the courtyard where you find Yukimura and Hanzo.
The Kushinada is not my favorite 5th weapon. Although it gives Kunoichi better Life, Musou, and the cool Ice element, it doesn't really appeal to you in any other way. I'm sure it's cool to know that with it Kunoichi will barely feel the pain of bullets and that she can jump even better than she already can (kinda overdoing it with the 2x Jump too?).
You're probably better off finding a really good 4th weapon. I currently use a Shiranui x8 with Lightning element, Attack +29, Life +25, and Agility +22. I find it to be a lot more usefull and found it on the exact same run as I did the 5th weapon.
Infiltration Tips
Samurai Warriors introduces a new infiltration mode where you play levels inside of buildings and are unaware of your surroundings. Your map unveils itself as you travel through the castle floors.
There are only a few infiltration maps so you can easily master the routes to reach your exit points. Missions on the levels however sometimes require you to search for other roaming officers and defeat them for mission completion points.
Samurai Warriors also introduces a new feature that allows your character to roll. By pressing R2, you can make your character roll past danger without recieving any injury. This is the method you should take when bypassing the closing spike wall and the flame thrower wall obstacles.
Costumes
Each character has two costumes you can play in. The second costumes are unlocked once you beat the character's Story Mode. You can change their costume with the "O" button. Some of them are very cool and others are just interesting. WARNING: Don't continue reading if you are afraid of spoilers and want to find out the costumes on your own.
Yukimura Sanada
1)Red samurai armor with matching headband
2)Full red samurai heavy gear with matching elk horned(?) helmet
Hanzo Hattori
1)Navy full body ninja uniform with hood
2)White karate uniform with same masked mouth but with hair exposed
Oichi
1)Cute white and pink outfit
2)Fox costume
Kenshin Uesugi
1)Black armor with white desert hood and pants
2)Blue outfit with blue crowned hood
Mitsuhide Akechi
1)Purple and white royal english style light armor
2)Dressed down in kimono with white pant wraps - hair in ponytail
Magoichi Saika
1)Black feather rimmed coat jacket with ammo shoulder strap (like Squall)
2)Nothing but pants and the ammo shoulder strap (wild look that drives girls crazy)
Masamune Date
1)Green medium armor with crecent horned helmet and eye patch.
2)White leopard skin outfit with matching boots. Cloth eye patch.
Shingen Takeda
1)Red, white, and grey outfit with red horned mask
2)A more wild version of outfit with gigantic freaky mask with big eyes
Keiji Maeda
1)Wild red and orange suit with chest exposed and wild Goku-like blond hair
2)Monk style octopus white robe and shaved head
Ranmaru Mori
1)Purple outfit (I know he looks like a girl, but it's supposed to be a young man!)
2)White school boy shirt with shorts and a cape. No comment. Nm, I actually like it now.
Kunoichi
1)Pink and white outfit with matching hat.
2)Ninja outfit - pink mouth cover and black leather armor. Way hot.
Okuni
1)White kimono blouse with long red dress
2)Short skirt outfit with long hair (drool - one of my favorite outfits)
Nouhime
1)Purple kimono dress with one leg explosed and coil leg jewelry
2)Short light patterned outfit with hair put up (hot outfit - just a little weird)