Just checked in here. Asked at the lounge about the reservations, and they gave me a letter with the details below on it (OCR'ed with an app on my phone, so excuse any errors...)
Dear Valued Guest,
It is our pleasure to welcome you to Hilton Tokyo. At Hilton, we always strive to improve our guests' experiences and are pleased to inform you that we will be expanding our Executive Lounge located on the 37th floor. Please be informed that the lounge will be closed for renovation from January 3 rd, 2019, and is expected to re-open by the end of April 2019.
The new lounge is designed with a modern Japanese theme. The seating capacity will increase by 1.5 times and will be split into three chic and timeless zones to cater for your business and leisure needs.
Mimicking the hotel's surroundings, the "Skyscraper" zone faces the business district and is where you will first enter the Lounge for check-in. We will also welcome you here every day for your complimentary breakfast, afternoon tea and evening pre-dinner cocktails. Sip a glass of wine alongside a stunning view overlooking the skyline of Shinjuku. This area is characterized by the elements of urbanization.
Our second zone "Nature & Park" faces the Shinjuku Central Park. This area is highlighted by the use of wooden furniture and earthy tones, as though you are away from the hustle and bustle of the city. This is where you can relax whlle enjoying views of the Central Park in all four seasons.
On to our last zone, "Sub Culture" combines the old and the new. This area represents the capital, Tokyo, where you can experience the essence of traditional Japanese interior design. Included are two semi-private library style rooms, and the simplistic modern Japanese design of the common areas.
With the renewal of our Executive Lounge, we will also be upgrading our current Executive rooms on levels 37 and 38 for a new look. While keeping the iconic Shoji Windows (Japanese Paper window), we will enhance the bathroom facilities and the interior designs which match the modern Japanese look and feel of the Executive Lounge.
For guests who will be staying with us during the renovation period, we are happy to offer the following alternate arrangements:
Check-in & Check-out Counters
Special check-in & check-out counter at the 1st floor front desk, only for our Hilton Honors Diamond members and guests staying in our Executive rooms and suites.
Breakfast
Your choice of the Executive breakfast in TSUNOHAZU on the 2nd floor dining space from 6:00am to 10:00am or intercontinental breakfast in Marble Lounge on the 1st floor from 6:30am to 10:30am (6:30am to 11:00am on weekends & national holidays).
Evening Pre-dinner Cocktails
Enjoy compiimentary drinks and hot/cold canapes at our ZATTA Bar & Lounge on the 2nd floor from 6:00pm to 8:00pm.