RYU GA GOTOKU ISHIN
Ryu ga Gotoku Ishin (released in Japan in February 2014) is a spin-off game set at the end of the Edo period of Japanese history (known as the Bakumatsu period), a period when the Tokugawa Shogunate came to an end and imperial rule was restored (Meiji Restoration).
Sakamoto Ryoma is living undercover, with a false identity, as "Saito Hajime" in Kyoto. One year earlier, on the eve of the coup d'état of Tosa, Ryoma's foster father, the man who raised him, was murdered before his eyes. The only lead he had to discover who the killer was is that he used the Tennen Rishin style of fighting. This is a style used by the Shinsengumi, so Ryoma infiltrates their ranks, becoming captain of the 3rd Shinsengumi unit, in attempt to find the killer.
Big thanks to Kevin Debrabandere for creating a PDF for the entire Ishin guide. You can download the PDF version of the guide here. Please be advised that the PDF is outdated now, but still contains information for the whole game.
This guide is for the original (2014) release of Ishin. The information contained within may not necessarily be accurate for the 2023 "Like a Dragon: Ishin" remake.
Equipment Symbols
Some weapons/armour have "symbols" which indicate the effect it has. When you synthesise a weapon with an "Empty" symbol with a weapon which has an effect symbol, the weapon takes that effect. For example, synthesising a sword with an empty symbol with the Matsukaze sword (which has the "Endurance" symbol) will fill the empty symbol of the base weapon with the "Endurance" effect from the Matsukaze symbol. This is good for customising weapons/armour to give it the effects you want.

Above is an example of a sword with a symbol

Above is an example of a sword that had an empty symbol and was synthesised with a sword with an effect symbol
Below are the symbols in the game:
Enhancement (Red)
In the battle dungeon, the corporal's soldier ability is enhanced
Swords: Himetsuru Hitomoji, Otenta
Greatswords: Yagyu Greatsword
Increases Experience acquisition
Swords: Dojisetsu
Pistols: Dragon Hawk
Spears: Gorinsai
Armour: Flower Design Headband
Makes it easier to fill the heat gauge
Swords: Sendai Kanemaru, Masamune
Pistols: Meikyo, Nichirin
Spears: Houten Spear
Armour: Symbol of Fighting Spirit
Fire a charged shot when you hold down the square button
Pistols: Heart Beat, Soul Beat
Enhances the effect of attribute attacks (blue symbols). For pistols, it enhances the effect of special attribute bullets
Pistols: Sakurabana, Shidarezakura
Spears: Large Brush
The more enemies you are fighting, the more powerful your attacks become
Swords: Senninsetsu
Greatswords: Large Saw
Enhances rapid firing speed
Pistols: Kazekumo, Kogarashi, Hayate
Cannon: Mechanical Cannon
Enhances rapid firing speed a lot
Fires 2 bullets with each shot
Pistols: Double Strike, Double Flash
Increases Hand-to-Hand Fighting Style attack power by 30%
Armour: Iron Gauntlet, War Fist Sarashi
Increases Hand-to-Hand Fighting Style attack power by 50%
Attack power and heat actions are enhanced when intoxicated
Makes it difficult for enemies to break free from your hold
Armour: Symbol of Super Strength
Attack power increases as health decreases
Armour: Symbol of Adversity
Reduces heat gauge consumption when using special techniques
Armour: Symbol of the Divine Dragon
Makes it easier to break an enemy's guard
Swords: Tepposetsu, Higesetsu, Onimaru
Pistols: Sword Crasher, Spirit Smasher
Greatswords: Large Hammer, Tenchisai
Makes it easier to hit enemies from a distance
Enemies are more likely to drop items
Swords: Golden Sword
Pistols: Golden Gun
The heat gauge automatically fills
The effects of praying at shrines are doubled
Armour: Double-Pilgrimage Talisman
Increases Dharma acquisition
Modification (Green)
Enemies are blown away when you hit with a big attack
Swords: Kijo Moji, Hidari Moji
Spears: Choukipaiko, Kagerosetsu
Cannon: Country Destroyer
Armour: Reppu
Pistols: Armor Breaker, Raging Bullet
Bestows the Blade attribute onto hand-to-hand attacks
(hand-to-hand attacks are treated as if they are sword attacks)
Increases enemy encounter rate
Stops the heat gauge from rising
Changes the circle attack function
(a special combo attack)
Changes the circle attack function
(a special combo attack)
Changes the circle attack function
(a special combo attack)
Slashing attacks cause a big wave
Attribute (Blue)
Makes it easier to break enemy armour
Swords: Suijinsetsu, Murasame
Swords: Shiranuhi, Okanehira
Greatswords: Bonbori
Cannon: Fenghuang
When attacking, surrounding enemies are blown away
Swords: Sakurafubuki, Morning Storm
Spears: White Dragon
Greatswords: Decorative Hagoita
Swords: Hotarumaru, Kaminarusetsu
Spears: Electric Stinger
Cannon: Electromagnetic Cannon
Swords: Tenkomaru, Mikazuki Munechika, Shining Konnyaku, Sohaya no Tsurugi
Swords: Juzumaru, Futsunotama
Armour: Snake
Absorb enemy health when you attack
Swords: Tokagemaru, Muramasa, Hanamori
Pistols: Non-Flying Bird, Spring in Full Bloom
Greatswords: Nenekirimaru
Protection (Yellow)
Enables you to defend against guns
Armour: Sacred Tree Gauntlet
Enables you to defend against bladed weapons
Increases resistance to attribute attacks
Armour: Hakuou, Divine Raiment
Some of the damage you receive is bounced back against the opponent
Spears: Large Chikuwa
Armour: Purgatory, Thorny Spider
Reduces the damage you receive from sword attacks
Armour: Blade-Proof Breastplate
Reduces the damage you receive from gun attacks
Armour: Fireman's Breastplate
Armour: Medical Herb Sarashi
Armour: Embroidery Headband
Health restores when you stand still
Reduces the amount of damage you receive
Swords: Matsukaze, Kogitsunemaru, Kogarasumaru, Lion King
Pistols: Nio, Kongo
Greatswords: Battleaxe
Armour: Brawler's Sarashi, Symbol of Will Power
Increases the speed at which you sober up
Alerts you to pot locations with a sound
Armour: Pot Sound Opportunity
You gain money as you walk around
Armour: Gion Hood, Ebisu Hat
Substory locations are indicated on the map
Reveals enemy locations on the map
Heat gauge automatically rises when you are at critical health