Quick Overview.
Senji at heart is an interesting mix of:

Area Control
Suit Matching Resource Gathering
Military Engagement
Diplomacy (Direct and through Mechanics)
VP Race
Special Abilities (From Samurais)
Leader Mechanic (Hosing the Emperor)

Components

Great artwork, high quality components, good size board with some obscurities in the rules.

Matt Drake has covered the main aspects of the game in a very truthfully humorous way (http://www.boardgamegeek.com/thread/327468) so I will address the game play psychologies that can really effect the enjoyment and overall play of the game.

Senji is in some ways similar to diplomacy (but less rigid) and has aspects very similar to Warrior Knights.

Game Psychology
It is a game of direct conflict from the beginning (Unlike Warrior Knights), there are no neutral zones so any military conflict will directly pit you against another player. This promotes an excessive amount of paranoia that must be stemmed unless you allow the Emporer Hosting player to run away with the VP by drawing hanafuda every turn. The map is quite simple and tight, but with sea raiding options and 2 sea areas that surround the map the chance for invasion from non-adjoining players becomes a real possibility. This is increased by the ‘raiding’ rules that allow a player to move twice and roll for minor losses as a penalty on entering the target province (1 in 6 per unit). Chained movement is allowed and military engagement are extremely brutal and very risky. Combine this and you have to be careful of a cold war starting between players allowing for domination by hanafuda collection.

However, once military actions are underway the mentality has to be to secure VP through attacks of domination to ensure victory. This means vicious backstabbing and isolation of players is essential in pushing out rivals often ending with 2 or 3 major factions.

Things swing wildly once military action really starts to flow but stabilises the relationships between the players. The use of family hostages is essential and sometimes allowing a player to kill a family member is worth the hit if they are near to winning and may lay the member to add the vp needed. The reality is that anyone is fair game and that VP scoring is paramount when the opportunity arises. If aggressive games do not appeal to a player then more often than not they will lose.

You cannot be a quiet player in Senji, a cowering mouse will just get stamped on, then ground into the dirt, then spat and finally defecated on. The Military stack limit means even if you are successful in taking a province do not expect to hold onto it for long as you cannot defend effectively with the cap of 12 military units. This again is a balancing technique to ensure no runaway leaders. However, this also means that more of the game is determined on the dice which may put a lot of players off. This can be controlled with the presence of Samurais and Military support which is critical to stemming the randomness. This is really interesting in that the whole thrust of the game is to control the random elements as much as possible by doing multiple trades with an ally rather than just picking hanafuda cards from production. Obtaining enough Samurais to cut down on randomness in battles (with some very interesting special abilities that can be critical) and ensure you have been effective in diplomacy to cover your arse from backstabbing as much as possible. If you do not want fate to decide you have to jump into the action and be part of the entire game.

There is in fact very little downtime as the complexities created from this essentially simple game keep you occupied while others fight. Desperate Pitt style diplomatic trading at the start is definitely a mistake but don’t hang around too long, if you have no allies you rarely can make it to the end in one piece.

The map only offers the minimal of strategic implication as there are no ‘special’ resource areas and only a minimal placement benefit for some houses. The sliding territory effect (player a attacks b is wins but is weakened then attacked by c) is lessened by the fact that if your military is decimated (which is usually is even if you win) the victory for the third party ( c ) is minimal usually only taking back a territory from you.

I think this game can be played very quickly, the hourglass makes diplomacy fast and furious to begin with then the game develops into trade exchanges and military support. It is not a game of over cautiousness as VP can be earned quickly by a decisive player.

Suffice to say I was crap at our first game and learnt a lot. I was static didn’t attack anyone and tried to draw hanafuda because I stupidly gave a 5 family member to the Host of the Emperor at the beginning precluding me from attacking him, most probably sealing everyone’s fate especially as the host was in control reaping the benefits by securing two border allies.

The trick of this game is ‘KILL THE HOST OF THE EMPEROR’ and don’t send Granny away so quickly.

A great mix of many games, streamlined into a blood thirsty, vicious orgy of backstabbing.