Starting May 23, 2026 (Saturday), the giant inflatable attraction THE MEGA JUMP MOUNTAIN JAPAN (MJMJ) at WHATAWON — a destination entertainment mall in Kishiwada, Osaka — will begin its water slide operation for the summer season.
This year, new giant slides and a large athletic area have been added, making MJMJ a bigger and more varied experience than last year. Water flows down the giant slides, sending splashes into the air on every run — a refreshing attraction well-suited to the summer heat.
The Evolved "New MJMJ" With Water Slides
The expansive inflatable area features a wide range of activities where children can run, jump, and bounce freely. The water-activated giant slides bring a soaking-wet element to the experience, and the attraction has been scaled up this year with both new slide sections and expanded athletic zones.
A Crowd-Pleaser Last Year on SNS
During the previous year's run, photos and videos of guests enjoying the water play spread widely on Instagram. Children sliding repeatedly while getting soaked, and families laughing through the splashes, made this attraction a well-known summertime spot. It works equally well for friend groups and weekend family outings.
Rentals and On-Site Items Available
Rental and retail items are available on site, so there is no need to come prepared with gear.
Rentals
- Life jacket (M/L sizes): ¥500
- Kids' swimwear: ¥500
- Face towel: ¥130
- Bath towel: ¥220
- Towel set (face towel + bath towel): ¥300
For Purchase
- Swim diapers
- Towels
Rentals and purchases are handled at Kyomachi Yuya SOKOTOTO inside WHATAWON.
Not Just Play — A Full Day Out at WHATAWON
WHATAWON is a destination entertainment mall with dining, shopping, events, and a dog run, among many other options. Visitors can relax at a café while kids play, spend time with pets, or enjoy the facilities at their own pace. It is a popular outing spot in southern Osaka for families and groups of all kinds.
Attraction Details
THE MEGA JUMP MOUNTAIN JAPAN (MJMJ)
- Water activation start date: May 23, 2026 (Saturday)
- Hours: 11:00 AM to 6:00 PM
- Location: WHATAWON grass area
- Address: 1-32-1 Kishino-oka-cho, Kishiwada City, Osaka
Admission Fees
Weekdays:
- Unlimited time: ¥900
Weekends, Holidays & Major Holiday Periods:
- 30 minutes: ¥600
- 1 hour: ¥1,000
- Extension (30 minutes): ¥550
Official website: https://whatawon.co.jp/newmjmj/
