Nobita loaned Suneo for 1000 yen, so Doraemon brings out the Memory Bank to let Nobita forget his home-run for 1000 yen, to the latter which can be anyways but... safe.
Spoiler alert! ↓ This section contains details concerning the progression of the plot, namely its result. If you do not want it to be spoiled for you, skip this section!
Nobita get the home-run in a baseball match, which the results overjoyed Doraemon. However, Nobita says that's isn't great, and says that he home-runned Suneo's recently purchased ball to a pond and he loaned Suneo for 1000 yen but Nobita has spended all of his money. Nobita almost cries, and Doraemon says that the luckiest of the unlucky, but told Nobita about it's better about keeping the home-run memory, and Nobita says that even better memories didn't turn into money. Doraemon then brings out the gadget, Memory Bank, despite that he didn't like to uses it.
Doraemon then explains uses this gadget, sell a memory for money. And if the memory were better the person have, the higher the selling price is. Then, Doraemon places the stick on Nobita's head, and search for the home-run memory and sells it for 1000 yen. Nobita holds the 1000 yen and says that he can give back Suneo, but before he asked why he must do that. Doraemon then says the gadget would forget what the user have after selling, and remembers that the Dorayaki big sale is held today.
Nobita purchased a new ball for Suneo and he thanked him. However when Suneo asks about Nobita's home-run, even not unaware of Nobita have forgetten it. Then, Nobita heads back home and uses the gadget to restore the memory bank, but needed to be paid in order to do so. And, Nobita was scolded by his mom for having bad grades... again. Nobita, however, having a idea to exhance the memory for money in order to restore the home-run memory back, but it needs to be paid 10 yen, but also his unlucky day memories. Until, Nobita found the great memories such of being praised by teacher and having picnic at moutains (Shizuka's food is soo delicious), and he sell these memories for 2000 yens and managed to restore the home-run memory back. Before the commercial break, Nobita remembers that Shizuka wants a new doll.
Nobita wents to Shizuka's home and asked Shizuka if she wants to sell memories for the new doll, but Dekisugi were also there. Then, the three were watching the gallery. They remembers having picnic at moutains and seeing the rainbows, but Nobita didn't remember it due to depoisted for 2000 yens with Memory Bank. Shizuka and Dekisugi learns of the Memory Bank, and Nobita asked if any memory to be sold, but Shizuka worries that the memories will disappears, but Nobita still not cares and explained the function of the gadget, and puts the straw opon Dekisugi's head. However, almost all of Dekisugi's memories were about 100% exam, nothing special, Nobita sold 80% exam memory for 3000 yen instead, but Dekisugi refused it because it was a better memory for him.
Nobita then went to the park and saws Gian and Suneo, and Suneo asked Nobita that he didn't give him recently purchased game that played by Gian first, but Nobita didn't cares. Nobita, at the Open Lot, using the gadget and search for his most expensive memories. However, he found that his memories with Doraemon, his friends, his parents and as well as his late grandma, were the most expensive memories...
Doraemon, shocked, heard that Nobita will earn money anytimes, anywhere, were heard from Suneo and Gian. Gian also says that Nobita hug the "strange thing" and Doraemon departs to the Open Lot where Nobita is, and the dorayaki packs were give to Suneo and Gian. Doraemon, worried, if Nobita really sold all of his memories only for himself turning into nothing. At Open Lot, Nobita were get caught by Doraemon, who cries for him that if Nobita really sold all of his important memories. However, when learned that Nobita just only sold his memories about he wants a new game for 2000 yen and they both went back home happily.
... but Nobita forget there's one thing to do: uses Memory Bank to sell his memories about his mother scolding him, but for the safety reasons, Doraemon refused to give him that gadget again.