Tokyo has two airports: Haneda (the old airport) & the more famous Narita airport (see map, above). Haneda is far more convenient but has fewer flights than Narita. The instructions below assume that you are attending both meetings and so expect you to arrive on February 7, say mid afternoon.
LODGINGS (February 7). You have two basic choices for February 7 overnight stay:
TRANSPORTATION (to IPMU) Kavli IPMU receives a large number of foreign visitors every year. They have a website which explains how to reach IPMU; see URL.
The train/subway/bus system in Tokyo is extensive and world class. A single IC card "SUICA" or "PASMO" can be used for all of these modes of transport (and also buying items from vending machines). At Narita airport please stop any information desk and collect maps etc. The "Yamanote" is the principal loop. Famous stations or important departure stations are Ueno, Tokyo, Shinagawa, Shinjuku and Ikebukuro. Since your first destination is IPMU I suggest that you take "Keisi Skyliner" to Ueno. From here you can go to Asakusa or Akihabara (which is the starting point for the fast train to Kashiwanoha Campus station). Also buy a "PASMO" or "SUICA" card and charge it up by, say, JPY 1000. [Upon departure you can return the card and get the initial deposit of JPY 500]. The website is exceedingly useful and helps you plan the trip. (It is is also an "app"; please install before departing to Japan].
AGENDA for Kavli IPMU meeting (Feb 8, 10a-3pm): To start with please see above URL to see how to reach IPMU either from downtown or from Kashiwa Mitsui hotel. We will start with a round-robin review of projects or missions in progress -- timeline, future plans for these facilities and also if funding/partnership is being sought: ZTF, DESI, PFS, KMTNet, IPAC, Tomo-e-Gozen, SRG, LCO, LAMOST, TAO, Gattini IR, LSST We will then have an open discussion until 3 pm when we leave to Nikko.