Re-enter Japan when no longer a student

Hi everyone,
Here are a few bullet points to summarize my situation:
- I am an exchange student at a university in Tokyo. My exchange program is until March 31, 2018, which is mentioned in my Certificate of Eligibility (CoE). When I entered Japan with a student visa, I got a residence card with a September 2018 expiration date.
- I technically have finished the exchange semester (done with all of my exams). I left Japan in February.
- I want to return to Japan in May for a trip and am just wondering if I can still re-enter the country with my residence card.
- I also got a special re-entry permit stapled to my passport when I left at Narita, even though the immigration officer told me I didn't need to get it. I also asked him if I can re-enter with my card after the exchange semester ends, he said yes but I need to find another school within 3 months or it'll become invalid.

I just want to make sure I will not have any trouble when I arrive in Japan in May. Or should I just get a tourist visa instead?
Thank you in advance.

You may get through but you wont know until the day of arrival. You are supposed to get into another school as per the student visa requirement. And if something doesn't go right at immigration, you cannot just change you mind and aim for a temp visitor instead. They'll deemed you lied to them and return you home. then you'll be banned from Japan for a period of time. I wouldn't risk it, I'd just come as a temp visitor.

you can come in with your residence card ...

but if they as you the reason .. just give them your reason... you never break any law.