Code Geass: Tales of an Alternate Shogunate

A Code Geass Elseworld manga by Ganji and Yoshijiro Muramatsu.

The year is 1853, Matthew Perry, using the power of Geass, forces Japan to open its ports to outsiders. Opposition arises in the form of the Black Knights, a resistance group that seeks to aid the oppressed citizens of Japan, led by the mysterious Zero. Meanwhile, Suzaku Kururugi, a low-ranking Samurai, tries to catch Zero despite the prejudice against him, not knowing that Zero's true identity is Lelouch Lamperouge, his friend who is head of the Shinsegumi. The introduction of the seventh-generation Knightmare Frame "Lancelot" has the potential to tip the balance of the conflict.

Tropes used in Code Geass: Tales of an Alternate Shogunate include:

Anachronism Stew: Pizza and Humongous Mecha in 19th Century Japan
Arson, Murder, and Jaywalking: “Thus the Japanese people lost their land… their pride… and even their topknots.”
Badass Arm-Fold: Lelouch in the Gawain.
Badass Normal: Suzaku, to perhaps an even greater extent than his other incarnations. He can even stand up to Knightmare Frames before he gets the Lancelot.
Beard of Evil: Perry
Big Bad: Perry
But Now I Must Go: Lelouch and C.C. leave Japan to Euphemia and Suzaku before disappearing
The Cameo: Milly and Shirley as clerks at the pizza shop.
Demoted to Extra: Several characters, notably The Emperor, who only gets a brief mention by Euphemia.
Detective Mole / Mole in Charge: Lelouch is in charge of the Shinsegumi, and the head of the Black Knights they are tasked with finding.
Enemy Mine: Euphemia’s forces and Lelouch’s ally to fight Perry
Excited Episode Title: "Defeat Perry! Japan opens up to the world at last!"
Evil Laugh: Perry, which doubles as an Annoying Laugh.
Fat Bastard: Perry.
Jerkass: Jeremiah mistreats Suzaku for letting Zero get away.
Killed Off for Real: Presumably Jeremiah
Historical Villain Upgrade: Perry
Humongous Mecha: They’re still present in the story, and Lelouch’s Geass now allows him to summon them.
Katanas Are Just Better: Suzaku wields one.
Kick the Dog: Matthew Perry shooting his own men with the Hadron cannon.
Lighter and Softer: The only named character to die is possibly Lord Jeremiah, and Lelouch and Suzaku are consistently heroic, albeit with different ideals, throughout the work. Even Matthew Perry is significantly less evil than the antagonists and some of the protagonists of the other incarnations.
Living with the Villain: Suzaku and Lelouch. Lelouch knows all along that Suzaku is his enemy, while Suzaku is unaware until shortly before they join forces.
Never My Fault: Jeremiah blames Suzaku for Zero's escape, although Lelouch claims that he let slip sensitive information. Then again, it's quite possible that Lelouch was actually the one responsible.
Won't Work On Me: Perry’s Geass powers don’t work on Suzaku, enabling him to force him to surrender.
Pose of Supplication: Perry's Geass victims, Suzaku when being punished by Jeremiah and Perry himself when he is defeated.
Samurai: Suzaku is introduced as a low-ranking Samurai
Schizo-Tech: Knightmare Frames aside, there are many pieces of overly advanced technology, such as radio communicators.
The Shinsegumi: Lelouch is their leader.
Smug Snake: Perry
Spared by the Adaptation: Everyone who died in the anime.
Transforming Mecha: The Black Ship
Villainous Breakdown: Perry, after the Britannian forces under Euphemia turn on him and again after he fails to Geass Suzaku
We Have Reserves: Perry’s mecha attacks his own troops.
Wham! Line

Suzaku: Zero, I understand your viewpoint. Then we should be able to work together. Zero... no... Lelouch.

What Could Have Been: Kallen sneaks into the creators’ offices and finds unfinished concept art. Nothing seems too out of place until she sees that Nunnally’s cart is equipped with hadron cannons.