The Man Who Died Seven Times by Yasuhiko Nishizawa

Hisataro is a mostly ordinary Japanese schoolboy, in his first year of high school in the mid-90s. Well, ordinary except for one thing: he relives the same day, over and over again, regularly but unexpectedly. By this point, he's worked out the rules: when a day repeats, it always happens exactly nine times. He's the only one who can alter what originally happened on repeated days, but what he does can make other people change what they did the first time around. He doesn't control when it happens, and it can happen multiple times in a week or not for a couple of months.

(He has, you might say, just a mild case of Groundhog Day syndrome, one that consistently clears up on its own without any need for medical or other intervention.)

So, at the point The Man Who Died Seven Times begins, Hisataro is physically sixteen - but he's lived through, he estimates, about twice as many years as that. It's given him advantages - acing tests that happen to land on repeat days, or using multiple days to get to know girls he wants to date - but mostly, he admits, he's a mediocre student without strong desires for anything, maybe a bit fatalistic because of his condition.

Seven Times takes place over one New Year's holiday, among Hisataro's family, mostly during one particular day repeating over and over again. And his grandfather keeps dying on that day - murdered, Hisataro thinks, by a member of the family. If he can just arrange events the right way on the last version of the day - the one that becomes "real" - then Hisataro can save his grandfather's life. 

He might be the only one that strongly invested in keeping the old man alive. Reijiro, that patriarch, was a bad father to his three daughters, especially after their mother died early. His oldest daughter ran off to college and married early to escape him; his youngest daughter married a teacher at her school soon afterward, also to escape. The middle daughter was left to keep care of him - and to become President and assumed heir of his company when an unlikely sequence of lucky bets and business ventures were wildly successful and the old man became very rich.

In the last few years - it's probably almost thirty years since those two daughters ran away - they've gotten closer as the old man got older. Everyone now spends the days after New Years at the old man's now-palatial house, reconfigured from how it was when the sisters grew up. 

Hisataro is the third of three sons of his mother; his aunt Haruna has two daughters. Their Grandfather is probably going to have one of those grandchildren adopted by his middle daughter Kotono, and so inherit the entire vast fortune. (Or, maybe, he'll have his faithful young assistant Ryuichi adopted instead - or even Emi, Kotono's assistant.) He writes a new will each New Year's, potentially changing his mind on his heir every time, though - before this fateful year - his family doesn't know all the details of how he decides and which heir he has decided on.

The whole family arrives - the five grandchildren and three sisters, but not the two husbands, who each bowed out for vague reasons related to problems each is having at work - on the 1st of January, to spend two days celebrating with family and then returning home the night of the 2nd. There's tension, as you'd expect, but mostly between the two runaway sisters, each maneuvering to set at least one of their children up for the fortune.

The days go normally; Hisataro remembers getting into the car to go home the evening of Jan 2, after a day of too much drinking with his grandfather. (There are a number of aspects of Seven Times that will seem really odd to North Americans; the casual way a sixteen-year-old gets absolutely blotto with his grandfather is the first and most obvious.)

But he wakes up in his grandfather's house. It's what he calls the Trap: the day will repeat nine times. And, in this first repeat, something shocking and unexpected happens: his grandfather dies, having his skull smashed in by a vase of flowers.

So Hisataro rearranges the next day so that the person who was with grandfather couldn't be - but grandfather is also dead at the end of the third version of the day, his head bashed in by that same vase.

And so on - Hisataro tries several times to gather as much of the family away from grandfather as possible, only to see him still die, still have a heavy object batter his skull, in versions four and five and six.

This is a play-fair mystery, so I won't give any more of the plot than that - I might have said too much already. Hisataro does solve the "mystery" in the end, and there is a plausible, fascinating twist even after he does solve it.

Nishizawa has a sly sense of humor here - this is not the kind of humorous book that has jokes, but there's dark amusement in the ways Grandfather keeps getting killed, and a different flavor of amusement in the infighting and maneuvers of the family members to get the old man's money. If you're looking for a mystery novel with an odd skiffy premise that makes strong use of both, Seven Times is a lot of fun.