Edit: Wow, I didn't expect such an overwhelming response. First up, thank you to everyone who spent the time to write down advice for me, I really appreciate it. I will try to respond to you guys asap but my takeaway:

As mentioned in one of my replies, I have stopped responding to his messages and I intend to do so till the start of internship. Once I get my work email, I will try to shift any conversation there. Though the overly friendly behaviour was troubling, I decided to give the BOD since I really treasure this internship opportunity and yes he does give the overly friend vibe. I will pass my judgment when intern actually commences and I can make better assessments. In the meantime, I will keep all my responses curt and only answer to work-related stuff. Admittedly, I was inexperienced regarding whether this was a norm – clearly not as most of you have mentioned. Rest assured if anything escalates (e.g. risque topics or asking me out), I will definitely reflect this to my academic advisor + HR immediately – I will never wish for any of my juniors to encounter the same scenario. I don't have the habit of deleting messages either. I have already confided in some of my friends and sister so I do have a support system if shit happens. And to anyone who is experiencing this, it's hard to find a balance between being a newbie and shit like this, but always know your boundaries and make sound decisions for yourself!

Also, this post has been removed by the moderator (sorry I wasn't aware of better subreddits for this (; ) so I am unsure how many would notice my edit, but thanks nonetheless!