In 東京, as everywhere in Japan, the everyday messenger is LINE, and the Japan guide shows how far its reach goes. A Tokyo plan that assumes WhatsApp will replace it will disappoint.
The plan that works starts with a question at first contact: which app do you use for business? Record the answer with the opt-in. The buyers, residents and travellers who say WhatsApp get your templates there; the rest you reach the way they asked.
Tokyo is three and a half hours ahead of India and never changes its clocks, so 09:00 in Tokyo is 05:30 in India. Updates a buyer is waiting for go when the event happens; anything promotional waits for Tokyo's working day.