It is Japanese tradition to visit a shrine on New Year’s Eve to purify one’s mind and soul before beginning a new year. On New Year’s Day, one will visit the shrine once again praying for a peaceful and healthy year, and this act is called Hatsu-Mode (literally translated as, the First Worship).
Natsu means summertime in Japanese so Natsu-Mode is the Summertime Worship. With half a year gone by, one will visit the Shrine again at the end of June to cleanse their sins they have accumulated through the first half of the year, and make another visit in the beginning of July to pray for peace and health for the second half of the year.