From here:
Growing older is pretty rough and Kenji is finding out just how hard it can be as life starts wearing down on him. On top of trying to make ends meet running a convenience store, he has to care for the niece that his missing sister left in his care. Memories of youth make it easier, until those memories come back to haunt you.

Kenji and his old friends are slowly being drawn into a mysterious conspiracy that could threaten the world. Who is the mysterious "friend", and how does he tie into Kenji's youth? Why are there disappearances and deaths tied into Ochanomizu University? The friend's memories hold the keys to the puzzle, but years between cloud the clues.

The strange occurances and the reach of the "friend" conspiracy grow by the day. It will all culminate on New Year's Eve 2000. Will Kenji and the rest of the group be able to put together the puzzle and save the world?

Note: The last two volumes of the story were serialized under the name 21st Century Boys and are not included here.

Monster weaves the riveting story of brilliant Dr. Kenzo Tenma, a famous surgeon with a promising career at a leading hospital. Tenma risks his reputation and promising career to save the life of a critically wounded young boy. Unbeknownst to him, this child is destined for a terrible fate.
A string of strange and mysterious murders begin to occur soon afterward, ones that professionally benefit Dr. Tenma, and he emerges as the primary suspect. Conspiracies, serial murders, and a scathing depiction of the underbelly of hospital politics are all masterfully woven together in this compelling manga thriller.

Note: Won the 46th Shogakukan Manga Award in the general category.

A one-shot side-story within the 1-volume Yawara! side-story, Jigoro!

A man and his daughter meet a mysterious man who has more than a few secrets and tall tales to tell about France and The Louvre Museum. What awaits for those who dare to follow their dreams?

(Source: MU)

A collection of 12 short stories published in one volume by Shogakukan in 1988. A fantasy about a middle-aged office worker who trains every day in order to become Japan's first astronaut. This work also includes earlier short stories, such as Beta!!.
(Source: Wikipedia)

A bunch of patients tries to covertly break out in order to eat ramen outside a hospital despite a strict curfew.

(Source: Batoto)

The one-shot opens with two slightly different members of a yakuza group talking together at a family restaurant. The yakuza group is in the middle of a dispute, and some members visit a young man named "Damiyan" who has a mysterious power.

(Source: ANN)

Growing older is pretty rough and Kenji is finding out just how hard it can be as life starts wearing down on him. On top of trying to make ends meet running a convenience store he has to care for the niece that his missing sister left in his care. Memories of youth make it easier, until those memories come back to haunt him
Picking up directly after the events of 20th Century Boys, it seems like the world is finally out of danger, but the mystery of "Friend" still exists. As the world is threatened again, Kenji must search his memories for any clue about "Friend".
(Source: ANN)

One day the Yakuza comes knocking on the door of the orphaned Umino siblings. The oldest brother has gone into hiding after acquiring a huge debt. Afraid for her brother, Miyuki agrees to take responsibility for the loan. The yakuza wants her to become a ho, Miyuki wants to be a tennis pro. Turns out she used to be a very promising player before her parents died. However, becoming a pro is difficult when friends are few and everybody else conspires to make Miyuki's life hell.

(Source: ANN)