お赤飯
赤飯 ([i]sekihan[/i], literally, red rice) is a mixture of glutinous [[rice]] and azuki beans that is steamed and eaten seasoned with sesame and salt. 
In Japan, it is customary to eat sekihan at any celebration. It is also widely canned as emergency rations due to its high nutritional value. 
Recipes and customs vary from region to region, with some regions having a tradition of eating sekihan after a misfortune, for example. 

At one time in Japan, a girl's first menstruation was celebrated by the entire family eating sekihan, often to the confusion of her younger siblings. 
Even now, after this custom has been abandoned, insinuation of a connection between the start of menstruation and sekihan sometimes appears manga as a running gag. In some cases ”the first menstruation” is replaced by ”the lost of virginity” to make things more funny. 

h4.See also 

* "Wikipedia article":http://en.wikipedia.org/wiki/Sekihan 
sekihan (tradition)