Banri didn't even know what his and Linda's relationship was. Perhaps he was afraid they were already a couple and thus he hesitated to approach her after he saw the pics. From the beginning of the show he has been pretty eager to get his first girlfriend, I'd say, but then he suddenly found out he might have had one before the accident. Since he's a very decent guy, he might have initially even felt a bit bad chasing Kouko if Linda was still technically his girlfriend.

Even though he hopes everybody would treat him as the new Banri, he's not stupid enough to expect that to happen. His family is the most troublesome lot of all, naturally, and the same ought to go for old friends. The worst detail of it all is that those people logically shouldn't mean anything to him. He's told they are his family, but he feels absolutely nothing, yet sees the desire in their faces. It's like an adult man absurdly adopted into a family without his own consent, just because he happens to look a lot like the family's original, dead son. Linda isn't any exception. Trying to treat him as a perfectly new acquaintance is underestimating his intelligence.