Have early breakfast and go to Shinjuku Bus Terminal (Busta Shinjuku) to catch the Fujikyu/Keio highway bus to Kawaguchiko; reserve seats online during busy seasons.
Start with breakfast and decide between Odaiba (bay area, teamLab Borderless alternatives, shopping) or Ikebukuro (Sunshine City, anime shops) depending on interest.
Odaiba: take Yurikamome Line from Shimbashi (uses IC card but Yurikamome special fare required); Ikebukuro: JR Yamanote Line direct. Check lines and fares beforehand.
Have dinner and prepare luggage and Shinkansen tickets for the following day's Tokyo→Osaka transfer. If you haven't already, consider booking Shinkansen seats today to secure preferred times.
Board the Tokaido Shinkansen from Tokyo Station to Shin-Osaka. Nozomi ~2h30 (fastest), Hikari ~3h00. Buy reserved-ticket at JR Midori no Madoguchi, ticket machines, SmartEX or JR online. Fare ~JPY14500 for unreserved/reserved (check exact fare/time).
Stroll the atmospheric streets of Gion and the riverside Pontocho alley for traditional town scenery and photo opportunities — no temple visits included.