An man who wakes up on a shore, having lost all his memory. Living in a village nearby, he doesn't really care about finding his past until a monster called an Unknown attacks, causing him to transform into Agito. He decides to use his power to protect his new life.
All Your Powers Combined: Trinity Form has body of Ground Form, but with arms of Storm Form and Fire Form. He can utilize weapons and powers from all three forms at once.
Deadly Upgrade: In A New Transformation TV Special, Shouichi has problem controling power of Burning Form when he first activate it. Ultimately subverted as he manage to control its power and transform into Shining Form.
A klutzy-yet-capable cop that becomes the main user of the G3-system. Though having a very bad first encounter with Agito due to him being berserk, he eventually joins forces with him and even Gills in protecting the city. His suit, the G3, was actually based on Unidentified Life Form # 4 aka Kuuga himself due to receiving data from two different prototypes and being originally created to fight Unidentified Life Forms. Though lagging behind temporarily, he eventually becomes competitive again with the help of a Mid-Season Upgrade in G3-X.
Cool Sword: GS-03 Destroyer. It's a high-frequency vibration blade and works more like a chainsaw in term of usage.
It's also completely ineffective - G3 never lands a successful hit with it.
Determinator: The G3 system can be worn by others, but it keeps coming back to Hikawa because, even when the chips are down or he's up against forces that greatly outnumber or overpower his own, he won't back down.
The Gunslinger: Japanese police officers don't have carte blanche to use, let alone carry, sidearms - the fact that Hikawa has a revolver on him at all times (and not no candy-ass snub-nose, either) says something.
Handguns: GM-01 Scorpion. Pretty weak, but easy to use, has good rate of fire and can be augmented with the GG-02 "Salamander" Grenade Launcher attachment.
Body Horror: First Rider to invoke it after Shin. Being Gills isn't something anyone would chose of their own free will.
Combat Tentacles: Played with. Gills has no control over his wrist tentacles beyond extension or retraction, and uses them only as striking weapons. Play straight as Exceed Gills, who can fully control them and has another set of tentacles from his shoulders as well.
Heel-Face Turn: His delusions of grandeur ultimately motivated him to try and eliminate others who had the Agito Seed and Kamen Rider Agito. It wasn't until his defeat at the hands of Exceed Gills and being saved from drowning that Kino became humbled. From that point on, he would aid the other Riders, even after the Overlord stole his power.
Heroic Sacrifice: In episode 46. Dies from the injuries he endured while performing a small surgery on Shouichi in an attempt to remove the quill of Ericius Liquor from his body, though he endured them long enough to join Agito and Gills in a Triple Rider Kick.
Mythology Gag: Deliberately resembles the original Double Riders, right down to the lack of weapons. The emphasis placed on his replaced right arm is also similar to Riderman's.
All There in the Manual: The individual names of the Lords are never given onscreen and can be found in supplemental materials. In fact, they're never even referred to as Lords, but rather as The Unknown.
Canis Latinicus: The naming pattern for the Lords, save for the El. Each name consists of two Latin words: genus + descriptor. Example: Pantheras Luteus = Leopard/Panther Saffron Yellow. Though, as to be expected, some translations can get blurred.
Even Evil Has Standards: They're specifically to target humans blessed with the seed of Agito (those whom have supernatural abilities). Killing normal humans (unless said human had committed murder) is a taboo and the penalty is forced suicide. The Ant Lords somehow bypass this rule.