One King Shogi

This variant was inspired by traditional Shogi problems (tsumeshogi), where only part of pieces is represented, with one king, wich must be checkmated in certain number of turns, and must be checked with every move (it's often important in shogi endgames, because of drop rule, wich can help to take the initiative in one move).

It also have some reference to "100 squares", novel by russian authoress Yulia Latynina, describing far planet with two civilizations, resembling medieval Europe and China, and having a chess-like game, named "100 squares".
In fact, i did not read this novel (maybe, i'll read it later), but, being avid chess variantist, i found text fragments, describing this game.
Game's rules are not detailed in the novel, but some key elements are known, and important element is only one King in center of board, and players are trying to influence Him. When Earth astronaut proposed that there could be two Kings, it was shocking to local chess player. Probably, Latynina was aware of Oriental chess forms, and the fact, why there are generals instead of kings in Xiang-Qi, and only one piece is named King in Shogi, while corresponding piece of the second player is "Jewel General".

Setup

Setup is just like in normal Shogi, but there are no kings on standart places. Instead, there is one neutral King in the center of board.

lhsg-gshl
-r-----b-
ppppppppp
---------
----K----
---------
PPPPPPPPP
-B-----R-
LHSG-GSHL

Rules

Rules are mostly as in normal Shogi. Either player may move the King, but only when he is in check by opponent. One may move king from attack by opponent's pieces under attack by own pieces.
It's possible to capture hostile pieces with the King (but not friendly ones).
Win by making position, where opponent can't move the King from your attack (checkmate) or where any opponent's move will put the King under you attack (stalemate).
And yes, it's not allowed to checkmate the King with pawn drop (as in normal Shogi).