Do you know this card? It is the "Ibaraki Kids Club Card" that is distributed to home having children under 18.
When you go shopping or restaurant with this card, you might get some service .For example, when you show this card at Kasumi, Jusco supermarket, you can get 5% discount on the 3rd Sunday. Masuda and Yamauchi's service day is the 3rd Saturday. I usually show this card at Drag Terashima (ドラッグてらしま) which sells not only medicine but also daily necessities, like shampoo, teeth brush, cosmetic items, baby staff.... When you buy over 2000 yen, you can get a box of tissues on Saturday and Sunday. I also have Drug Terashima's Family Card, and go there on Monday or Friday to get double points. (You can get 1point when you buy 105 yen usually. If you get 500 points, it pays you back 300 yen as a discount ticket. ) Map of Drug Terashima in Tsukuba
Showing the card at"McDonald's", it sells cheese burger happy set for 350 yen, and
"mister Donut" gives you 10% discount when you buy donuts up to ten.
You can check other restaurants and shops that give discount when you show the card.
If you don't have this card, or lost the card, you can get it at the Tsukuba city office (桜庁舎 こども課).
Web site : http://www.kids.pref.ibaraki.jp/kids/pc/