Responses
He didn't say Sachi is the only one he'll ever love, he actually said he'll always love Sachi, but Bambi is the one he loves now and wants to spend the his life with her.
That's not at all what he said, read it again.
I think Bambi should just be friends with Tetsu. Why the heck would he tell Bambi Sachi is the only one he'll ever love ?