The 4th Raikage is a red taijutsu ninja that can be gained in Pockie Ninja 2 Social.
4th Raikage (named A in the anime) appears in his outfit during the Five Kage Summit in Naruto Shippuden. He is bare-chested, revealing a large muscular build. He wears gold bangle bracelets, similar to oversized metal arm bands, and a gold belt around his waist, giving him the appearance of a professional wrestler. He also wears black pants and has bleach-blonde hair.
4th Raikage is a formidable taijutsu ninja, who relies more on attack than HP. At Level 20, he can learn the Arhat Fist, which deals 80% attack and stuns the target for 1 turn. Because he is more of an attacking ninja, he would normally be equipped with Ultimate Crush, Ultimate Rasen Shuriken, or Grand Rasengan.
The 4th Raikage is definitely a punisher, so he should be in the front line, taking down weapon ninjas. Equipping him with Ultimate Rasen Shuriken (deals 250% attack but sacrifices 30% max HP), Grand Rasengan (deals 150% attack + 162 damage, and has 2 tries), and Ultimate Crush (deals 180% attack + 243 damage). Make sure you have enough tankers to take hits for the 4th Raikage while he deals massive damage upon the enemy.
You can get the 4th Raikage using Red Ninja Packs (though chances of getting him are rather small), Ninja School (must be at least Lvl. 7 to have a decent chance of getting red ninjas), and through Trial, where you can win Red Ninja Packs on the lucky draws every 10 levels. You can also get him at Hinata's Storage Box, where a Red Ninja Pack is always one of the prizes, though getting this is quite rare.