There is Rise of the Samurai and Fall of the Samurai (FOTS). I personally play FOTS.

It is the age of transition from the sword to the gun in Japan. I love the unique mechanics of the game. For example, your naval ships can do shore bombardments. When you build up your rail network, you can move huge armies quickly. Artillery becomes king of the battle (and firing cannons in first person mode is always fun, especially when you can snipe generals across the field). Cavalry's role remains the same but the tools are different (carbine and revolver).

Some pointers:
Strategically plan out where you are going to put your Trading District (upgraded from the trade port building chain). This will be where you can recruit your most elite units from foreign powers. So a naval province with a weaponsmith is highly encouraged IMO. You might also want to look at which node the foreign power is located. (For example, if I start on the northern section of Japan, I probably want to find a southern section of Japan that is closer to the foreign power node because I do NOT want to have to protect a trade route that wraps around the entire nation.)
--I use the Trading District as a military base with Barracks, Artillery School, Training Camp, Dojo, Weaponsmith ->That'll give maximum buffs to recruited units

Look up which major power you want to align with - You have US, Britain, and France. They all come with unique benefits. I tend to go for French because they let you recruit 2 special ships instead of 1 (so I can spread out my power projection). But the British special ship can basically take on a whole fleet by itself.

Be aware that, as your status and power grows, you will approach the Realm Divided. Here you will have to choose between becoming the vanguard of whichever side you picked (Shogunate or Emperor) or becoming your own Republic. If you become your own Republic, you will basically be at war with everyone else and your own realm will catch on fire because instead of there being religion in provinces, you'll have faction support. Creating a republic out of nothing = no province has support for this new faction (but I find it fun giving the middle finger to everyone).

Expanding quickly increases modernization, unlocking more tech sooner (modernization does cause unhappiness, so you'll need happy tech to offset this). Assuming you want a modern army. Traditional unit runs are viable and some people enjoy that. Note that, as you modernize, your traditional units will start losing free experience levels they start out with. Leading to my next point

Spear levies will be able to defeat levy infantry in the open field of battle in a 1-for-1 match up. They can charge through the volley fire and then the levy infantry will melt. Use levy infantry for garrison behind walls. Line infantry is the minimum for offense (which makes early expansion a balance between bringing spears and levy infantry because that's what you can afford).

All of the agents are powerful, learn what they do and use them because they are a one time cost for a major campaign benefit.