Line age verification, 2nd hand phone?

I bought an unlocked phone second-hand from a person who I don't even know how to contact now. It was through craigslist. They originally bought it from docomo, but since it's unlocked I am now using a sim card from IIJmio. (The sim card only just arrived today.)

LINE is my only method of contacting all my friends in the country I lived in before because they all work long hours and just don't have time for social networking and writing long e-mails. LINE is quick and easy. I want it on my new phone, but I can't even open it at all without passing the age verification. It sends me to a docomo website to do this, where I need to put in a docomo phone number and password that was supposedly created at the time of buying the phone and signing a contract. It's impossible for me to know the phone number and password this other person set for the phone, so what on earth do I do now?

Have you tried contacting docomo?

for security reason line verification/signin required a valid mobile phone no for registration.
that yhe suxx thing about buying 2nd hand phone in Japan, havong all those 'INf convenience provider bloatware that is convenoence if ypu signup with origina/ provider but become inconvenience iusef 2nd hand with other provider.

you will not be able to get through it amd most probably the original phone no./accouny have been discontinue /cancrlled.

try login using your old account. or registered with other phone no. that you have.

Thanks for the replies.

You're right, it seems there's no way around it. I used what Japanese I know to go to the docomo ID website, register myself for a docomo ID and I then tried the age verification for Line (as I did have to give my date of birth on ID creation) with my ID and password, but it gave me a message that seemed to say only an ID from buying a 2-year contract with docomo would work. Looks like I'm stuck keeping my old phone to stay in contact with my friends.

Did you factory reset the phone?
I have a phone with iijmio sim and I can use Line. I can't verify my age either but as far as I know the only thing I miss without it is the search-by-id feature.

How did you manage to actually use Line without doing the age verification? I cannot use it at all without doing it because every time I press `skip', it tells me there was an error.

Sorry, forgot to mention I have factory reset it and still have the same issue.

I don't know why you're having trouble with it. I just installed it and it worked. It didn't required me to do the age verification. It's optional on my phone.