Lufthansa cancelled one leg of my itinerary. Can I ask for a partial refund?

I had a roundtrip booking for USA-GER-IN1-IN2, where USA is a US airport, GER is a German airport, and IN1 and IN2 are Indian airports. I received an email that the IN1-IN2 legs (both inbound and outbound) have been cancelled. The email offers two options: (a) keep the USA-GER-IN1 roundtrip or (b) cancel the entire trip and receive a full refund.

I would like to keep the USA-GER-IN1 roundtrip but also request a partial refund for the cancelled IN1-IN2 leg. Do you think that this is a reasonable request to make and that Lufthansa will honor this request?