[5] Introduced in 1957, the Odakyu 3000 series SE Romancecar and associated Hakone limited express service proved to be very popular, and there were capacity shortages on weekends even with all trainsets in use.

[9] Ahead of the 1964 Tokyo Olympics, different plans to increase the capacity of Romancecars were considered, which included building new 3000 series sets, lengthening existing ones, or manufacturing a new vehicle.

Odakyu chose the latter,[10] based on the idea that "the limited express vehicle is the icon of the company and must give passengers dreams with its novelty and splendor.

[6] While the 3000 series was a leap in technical performance compared when it was introduced, it was viewed as "somewhat poor" by the Odakyu sales department.

[6] This was in part due to the 3000 series' focus on weight reduction, whereas new limited express trains by other railway operators emphasized novelty and luxury.

[15] The additional trainsets enabled Odakyu to introduce a schedule update in November, which adopted a 30-minute headway for Hakone services and cut trip times between Shinjuku and Odawara down to 62 minutes.

[20] This included a new lighting arrangement, double glazed passenger windows, and a change of the front service sign from an acrylic plate to an electronic rollsign.

[24] Regular Romancecar service concluded on July 16, 1999,[25] with a ceremony at Hakone-Yumoto, the first and only time a 3100 series trainset would depart from the station.

[27] In October 2017, due to increased train storage requirements ahead of the completion of a quadruple tracking project on the Odawara Line, three intermediate cars from the set were to be dismantled.