ドキドキ (dokidoki): a feeling of excited anticipation, but usually one with a sense of anxiety or rapid heartbeat.

You use dokidoki when you're feeling nervous, uncertain, or possibly scared about something that's coming. The feeling is linked to a quickening pulse. You don't know if the thing coming will be good or bad.

Example: Hana is waiting for her exam results. She dokidoki whispers, “I hope I passed.” The outcome she awaits is crucial, and she's extremely worried until she knows for sure.

Use wakuwaku when you are delighted about something you are eagerly anticipating. This anticipation does not carry the same degree of anxiety as dokidoki, but rather a more innocent sense of thrill and pleasure.

Example: Kenji has finally saved enough money to go to his favorite theme park. He is wakuwaku because he knows the trip will be filled with fun, and he is sure that he will greatly enjoy himself. Wakuwaku may have a bit of a nervous edge, but excitement is its chief characteristic.

ワクワク (wakuwaku) shares some qualities with the expression キラキラ (kirakira), but their application is different.

キラキラ (kirakira): represents a sparkling or glittering quality, or things that shine.

You would choose kirakira to describe something shiny or to describe a person’s eyes that are sparkling with happiness.

Example: Aiko is looking at the Christmas lights strung on her house. She thinks to herself, "Oh, how kirakira!"

Kirakira does not have the same nuance as wakuwaku, which is attached to emotional states. One feels wakuwaku; one sees kirakira.

Example: Take the same situation as Kenji above, but change the scenario.

If Kenji is wakuwaku, he is excited about the activities he plans in the theme park. But if he is kirakira, it is because some aspect of the park is particularly shiny or glittery, perhaps the lights on a parade float. In this context, wakuwaku would be more fitting!